bluuebunny/crossref_metadata_2025 huggingface dataset:
Blood pressure and acidic renin forms in stroke-prone hypertensive rats
Authors: Lee J. , Malvin R. L. , Jokelainen P. T.
Published: December 2017

Six forms of renin, distinguishable by their isoelectric focusing characteristics, are found in rat kidney and plasma (forms 1-6, form 1 having the most basic pI). To test the hypothesis that high blood pressure in stroke-prone spontaneously hypertensive rats (SHRSP) is associated with a particular fraction of the renin forms, systolic blood pressure (SBP) and renin profile were measured in SHRSP, normotensive Wistar-Kyoto rats (WKY), and their genetic crosses (F1). Adult SHRSP showed an increase in the proportion of forms 4, 5, and 6 compared with WKY. F1 showed values between SHRSP and WKY. A strong positive correlation was noted between the fraction of the acidic forms of renin and SBP. The mean blood pressure and the fraction of the acidic renin forms in SHRSP and WKY pups also fitted the same regression line. However, no correlation existed between renal renin content (RRC) and SBP. SHRSP pups had a higher RRC than age-matched WKY or F1. RRC in normal adult SHRSP was lower than that in WKY or F1 of the same age. In old animals, SHRSP again showed the highest RRC, and microangiography of the kidney of old SHRSP revealed a loss of fine vascularity with few visible glomeruli. These results indicate that the established phase of hypertension in SHRSP is associated with an increased proportion of the acidic forms of renin, which may have a unique role in the establishment or maintenance of hypertension. It is also suggested that high RRC in the early developmental stage plays a role in the developing phase of hypertension.
Effect of changes in sodium or water intake on glomerular B2-kinin-binding sites
Authors: Emond C. , Bascands J. L. , Cabos-Boutot G. , Pecher C. , Girolami J. P.
Published: December 2017

In a previous study, we characterized a B2-kinin-binding site in rat glomerular membranes. We have now investigated the density and affinity of this binding site for bradykinin (BK) in rat glomerular membranes, in relation to the renal and urinary levels of kallikrein during changes in sodium and water intake. The density of BK-binding sites was reduced after 28 days of low-sodium diet (12.5 +/- 1.3 vs. control: 32.1 +/- 5.2 fmol/mg protein, P less than 0.05), whereas the concentration and activity of kallikrein was increased in the renal tissue and in the urine. Water deprivation for 4 days also resulted in a decreased density of binding sites (13.2 +/- 1.2 vs. control 32.1 +/- 5.2 fmol/mg protein, P less than 0.05) and, interestingly, renal kallikrein levels increased. During high salt consumption, urinary kallikrein activity increased but the renal concentration and activity of kallikrein was unchanged. In this high-sodium-loaded group, BK-binding site density was similar to controls receiving a normal-sodium diet (41.6 +/- 8.4 vs. control 32.1 +/- 5.2 fmol/mg protein). On the other hand, the binding affinity of BK did not change significantly in all experimental groups, and the binding specificity was not altered as BK remained the most potent agonist. Sodium depletion and water deprivation led to the same effects on BK-binding sites and on renal kallikrein. The renal glomerular BK-binding site density decreased in both conditions, whereas the renal level of kallikrein was enhanced. An inverse relationship between renal kinin levels and the density of glomerular BK-binding sites is therefore suggested.
Mitogenic signals for thrombin in mesangial cells: regulation of phospholipase C and PDGF genes
Authors: Shultz P. J. , Knauss T. C. , Mene P. , Abboud H. E.
Published: December 2017

Thrombin is a proteolytic enzyme of diverse biological activities, which is produced during activation of the coagulation pathway. In addition, thrombin is a mitogen for fibroblasts and endothelial cells. Intraglomerular thrombosis and cell proliferation are common pathological features of several glomerular diseases. We studied the effect of thrombin on deoxyribonucleic acid (DNA) synthesis in cultured human mesangial cells and explored mechanisms of signal transduction involved. Bovine and human thrombin caused dose-dependent increases in DNA synthesis, inositol trisphosphate, and cytosolic calcium [(Ca2+)i]. A threefold increase in inositol-3-trisphosphate (IP3) levels was observed as early as 10 s after the addition of thrombin, whereas increases in (Ca2+)i occurred within 5-10 s and declined rapidly. Stimulation of mesangial cells by thrombin resulted in induction of messenger ribonucleic acids (mRNAs) encoding platelet-derived growth factor (PDGF) A- and B-chains. This was associated with an enhanced secretion of PDGF-like protein. These data provide mechanisms by which thrombin may regulate mesangial cell function in disease states.
Immunocytochemical localization of intracellular acidic compartments: rat proximal nephron
Authors: Verlander J. W. , Madsen K. M. , Larsson L. , Cannon J. K. , Tisher C. C.
Published: December 2017

There is evidence that components of the endosomal-lysosomal system of most cells have an acidic interior. The weak base, N-(3-[(2,4-dinitrophenyl)amino]propyl)-N-(3-aminopropyl)methylamine dihydrochloride (DAMP) has been shown to accumulate in acidic compartments in cultured cells and in isolated perfused proximal tubules. We infused DAMP intravascularly in vivo and used colloidal gold immunocytochemistry to identify acidic compartments in cells of the rat glomerulus and proximal tubule. Sprague-Dawley rats were infused intra-arterially with DAMP. The kidneys were fixed by intravascular perfusion with 1% glutaraldehyde and embedded in Lowicryl K4M. Sections were exposed to a mouse anti-dinitrophenol (DNP) monoclonal antibody that cross-reacts with DAMP, followed by gold-conjugated goat anti-mouse immunoglobulin G. Transmission electron microscopy revealed positive labeling of the lysosome-like structures of the various cells of the glomerulus and lysosomes, endosomes, and numerous endocytic vesicles of all segments of the proximal tubule. We conclude that 1) DAMP can be used in vivo to identify acidic compartments in the kidney and 2) lysosomes, endosomes, and many endocytic vesicles of the rat proximal tubule as well as lysosome-like structures in cells of the glomerulus have an acidic interior.
Atrial natriuretic factor binding sites in experimental congestive heart failure
Authors: Bianchi C. , Thibault G. , Wrobel-Konrad E. , De Lean A. , Genest J. , Cantin M.
Published: December 2017

A quantitative in vitro autoradiographic study was performed on the aorta, renal glomeruli, and adrenal cortex of cardiomyopathic hamsters in various stages of heart failure and correlated, in some instances, with in vivo autoradiography. The results indicate virtually no correlation between the degree of congestive heart failure and the density of 125I-labeled atrial natriuretic factor [(Ser99, Tyr126)ANF] binding sites (Bmax) in the tissues examined. Whereas the Bmax was increased in the thoracic aorta in moderate and severe heart failure, there were no significant changes in the zona glomerulosa. The renal glomeruli Bmax was lower in mild and moderate heart failure compared with control and severe heart failure. The proportion of ANF B- and C-receptors was also evaluated in sections of the aorta, adrenal, and kidney of control and cardiomyopathic hamsters with severe heart failure. (Arg102, Cys121)ANF [des-(Gln113, Ser114, Gly115, Leu116, Gly117) NH2] (C-ANF) at 10(-6) M displaced approximately 505 of (Ser99, Tyr126)125I-ANF bound in the aorta and renal glomeruli and approximately 20% in the adrenal zona glomerulosa in both series of animals. These results suggest that ANF may exert a buffering effect on the vasoconstriction of heart failure and to a certain extent may inhibit aldosterone secretion. The impairment of renal sodium excretion does not appear to be related to glomerular ANF binding sites at any stage of the disease.
Mediated transport of long-chain fatty acids by rat renal basolateral membranes
Authors: Trimble M. E.
Published: December 2017

Transport of long-chain fatty acids (LCFA) was studied in isolated rat renal cortical membrane vesicles to determine the mechanism of entry of these metabolic substrates into renal cells. Total uptake of palmitate into basolateral (BLMV) and brush-border membrane vesicles (BBMV) was determined with the use of a rapid filtration technique. In the presence of an inwardly directed H+ gradient (pHo = 6.0, pHi = 7.4) palmitate (0.26 microM) uptake went through a maximum (“overshoot”) in BLMV but not in BBMV. The amount of palmitate nonspecifically bound to vesicles was subtracted from total uptake to determine intravesicular content. Peak values for intravesicular palmitate content were 26 +/- 9 pmol/mg protein, 2.5-fold higher than 60-min values of 10 +/- 2 pmol/mg (P less than 0.05, n = 6). The overshoot could not be accounted for by changes in voltage. An inwardly directed Na+ gradient was without effect on palmitate uptake in BLMV and BBMV. pH gradient-stimulated palmitate transport (15 s) in BLMV was subject to cis-inhibition by 4,4'-diisothiocyanatostilbene-,,2-disulfonic acid. Probenecid and p-aminohippurate efflux from BLMV resulted in counter-flow accumulation of palmitate. It is concluded that at least a portion of LCFA transport across the basolateral membrane is mediated and may occur via anion exchange.
Protein kinase A, cytosolic calcium, and phosphate uptake in human proximal renal cells
Authors: Middleton J. P. , Dunham C. B. , Onorato J. J. , Sens D. A. , Dennis V. W.
Published: December 2017

Phosphate uptake by proximal renal cells derived from the human kidney occurs by a saturable process that is approximately 85% dependent on the presence of sodium. Kinetic analysis is consistent with two distinct transport events with Km of 0.08 and 0.63 mM and Vmax of 3.4 and 11.0 nmol.mg-1.3 min-1, respectively. Parathyroid hormone (PTH), isoproterenol, and prostaglandin E2 (PGE2) increased cellular adenosine 3',5'-cyclic monophosphate (cAMP). PTH-stimulated cAMP prevented binding of the photolabel 8-azido[32P]cAMP with a half-maximal effective concentration (EC50) of 1 nM PTH, 30-fold lower than the EC50 for intracellular cAMP accumulation. These data are qualitatively similar to those observed in OK cells. PTH did not inhibit phosphate uptake in human cells, although it activated cAMP-dependent protein kinase and increased cytosolic calcium. Thus phosphate uptake in human proximal renal cells maintained in short-term culture is unresponsive to PTH in spite of increased cytosolic calcium and activation of the cAMP pathway.
Effect of antidiuretic hormone on renal organic osmolytes in Brattleboro rats
Authors: Schmolke M. , Beck F. X. , Guder W. G.
Published: December 2017

Homozygous Brattleboro rats were used to study the effect of antidiuretic hormone (ADH) on organic osmolytes, which have been shown to be involved in the cellular osmoadaptation in renal inner medulla. With the use of enzymatic spectrophotometric methods, glycerophosphorylcholine, sorbitol, and inositol were determined in kidney sections from papillary tip (IM3) to cortex. Compared with normal rat kidneys, IM3 of untreated Brattleboro rats (urine osmolality 132 mosmol/kg) were sorbitol depleted (16 +/- 1 vs. 371 +/- 37 mumol/g protein) and glycerophosphorylcholine was reduced to 20% (131 +/- 16 vs. 658 +/- 52 mumol/g protein). In contrast inositol was not changed (147 +/- 25 vs. 177 +/- 29 mumol/g protein). Similar effects were obtained in all medullary sections. Continuous treatment with ADH increased urine osmolality already after 5 h but renal glycerophosphorylcholine and sorbitol content only after 24 h. Normal osmolyte levels were reached after 3 days of ADH treatment when urine osmolality was 1,595 mosmol/kg. Inositol did not exhibit comparable changes during ADH treatment. The present results indicate that ADH, possibly by increasing interstitial tonicity, leads to increased glycerophosphorylcholine and sorbitol, but not inositol, contents.
Evidence for cholinergic innervation in dog renal tissue
Authors: Pirola C. J. , Alvarez A. L. , Balda M. S. , Finkielman S. , Nahmod V. E.
Published: December 2017

Denervation procedures that affect the sympathetic system of the kidney, as demonstrated by norepinephrine depletion of renal tissue, increased urine volume, fractional sodium excretion, and free water clearance in anesthetized water-loaded dogs. These increases were reduced by atropine, which also blocked the increase above those basal functional levels produced by acetylcholine in both innervated and denervated kidneys. An in vitro tubular cell preparation of innervated kidneys corresponding to the outer cortex showed [3H]quinuclidinyl benzilate (QNB) binding parameters characteristic of muscarinic receptors. Denervation did not change either [3H]QNB binding parameters or the ability of inner and outer cortex cells to perform the hemicholinium-3-inhibitable, sodium-dependent choline uptake and conversion of [3H]choline to [3H]acetylcholine. This cell membrane behavior is similar to that observed in tissues where cholinergic neuronal structures are present, suggesting the existence of a cholinergic innervation of the kidney, independent of the integrity of vessel-traveling nerves. Similarly, the finding of choline acetyltransferase in renal tissue, unaffected by sympathetic denervation, seems to confirm the presence of cholinergic nerve terminals. The cholinergic system may thus contribute to the regulation of tubular reabsorption of sodium and water in some conditions.
Renal vascular responses and eicosanoid release in diabetic rats
Authors: Sarubbi D. , McGiff J. C. , Quilley J.
Published: December 2017

Changes in renal perfusion pressure and eicosanoid release in response to arginine vasopressin (AVP; 1-10 ng) and angiotensin II (ANG II; 1-10 ng) were determined 5 days, 2 wk, and 8-12 wk after the induction of diabetes with streptozotocin (STZ) in male Wistar rats. Renal perfusion pressure responses to AVP and ANG II were reduced at 2 and 8-12 wk, but not at 5 days, after the induction of diabetes. However, AVP- and ANG II-stimulated release of prostaglandins into the renal venous effluent was depressed at all times tested. Inhibition of cyclooxygenase with indomethacin did not significantly influence the perfusion pressure responses to ANG II and AVP. Likewise, raising perfusate glucose levels to 400 mg/dl or adding insulin (180 microU/ml) to the perfusate failed to modify responses to ANG II. In contrast, administration of 0.3 microgram arachidonic acid (AA), a dose approaching threshold in control rat kidneys, to the kidney of the diabetic rat resulted in a marked increase in perfusion pressure. Associated with the increase in renal perfusion pressure to AA in the diabetic rat were significant increases in renal venous efflux of prostaglandin E2 and prostacyclin compared with control. These data suggest a defect in renal deacylation-reacylation of AA associated with an increase in cyclooxygenase activity in the diabetic rat.
Rat mesangial cells produce granulocyte-macrophage colony-stimulating factor
Authors: Budde K. , Coleman D. L. , Lacy J. , Sterzel R. B.
Published: December 2017

Because inflammatory processes in renal glomeruli may involve monocyte-macrophages (MPs) and T-lymphocytes, we have investigated whether products of glomerular mesangial cells (MCs) can stimulate the proliferative activity of these effector cells. We found that cultured rat MCs (subcultures 2–15), maintained under serum-free conditions, secrete a soluble factor into the supernate [MC-conditioned medium (CM)], which supports growth of the T-helper cell-derived line HT-2. Moreover, MC-CM increased [3H]thymidine incorporation by thioglycollate-elicited peritoneal MPs but did not induce growth of the interleukin 2 (IL-2)- or interleukin 4 (IL-4)-dependent cell line CTLL-2. Further functional, serological, and biochemical analysis of MC-CM revealed that rat MCs secrete a cytokine that, by all of the techniques used, is indistinguishable from granulocyte-macrophage colony-stimulating factor (GM-CSF). Both northern blot and in situ hybridization with a specific cDNA probe for murine GM-CSF showed that MCs express GM-CSF mRNA transcripts. The present findings indicate that cultured rat MCs produce GM-CSF. Release of GM-CSF by MCs in vivo may play a role in the interaction of MCs with MPs, T-cells, and neutrophils in glomerular disease.
The growth hormone-insulin-like growth factor axis in kidney
Authors: Hammerman Marc R.
Published: December 2017

Pages F503-F514: Marc R. Hammerman. “The growth hormone-insulin-like growth factor axis in kidney.” Page F508: We regret that the colors in some of the reproductions of Fig. 6 are not faithful to the original.
Effects of xanthine oxidase inhibition on ischemic acute renal failure in the rat
Authors: Zager R. A. , Gmur D. J.
Published: December 2017

To assess the effects of xanthine oxidase (XO) inhibition on ischemic injury, rats were pretreated with oxypurinol (OXY, 5 mg/kg) and subjected to 30 min of bilateral renal artery occlusion. OXY's effect on adenine nucleotide-nucleoside-purine base concentrations was determined at 10 and 30 min of ischemia and during reperfusion (5 and 30 min). To assess whether XO-mediated oxidant stress influences the severity of ischemic acute renal failure (IARF), the effects of 1) OXY pretreatment and 2) hypoxanthine infusion were assessed. During ischemia OXY inhibited XO activity (more than fourfold rise in hypoxanthine-xanthine ratios) and induced quantitatively trivial but significant increases in ATP and total adenine nucleotide concentrations (by 30 min). Increased OXY dosage (15 mg/kg) or allopurinol (40 mg/kg) had no greater effects. At 5 min of reflow, OXY maintained XO inhibition but did not influence adenine nucleotide levels. By 30 min of reflow, 17–20% increments in ATP-total adenine nucleotides resulted. Nevertheless, OXY did not lessen the severity of IARF (assessed by azotemia-histology at 24 h). Hypoxanthine infusion increased end-ischemic hypoxanthine concentrations by 47%, but it did not change the severity of renal damage. Conclusions include 1) OXY-allopurinol induces intrarenal XO inhibition; 2) XO inhibitors slightly increase late ischemic-reperfusion adenine nucleotide concentrations; and 3) neither XO inhibition nor intrarenal hypoxanthine loading alters the severity of IARF, suggesting that XO-mediated oxidant stress is not a critical, consistent mediator of ischemic renal injury.
Sodium chloride and water transport in the thin descending limb of Henle of the quail
Authors: Nishimura H. , Koseki C. , Imai M. , Braun E. J.
Published: December 2017

Birds and mammals can produce hyperosmotic urine, but their renal morphology and urine-concentrating mechanisms differ. To elucidate the countercurrent urine concentration mechanism in birds, we examined the structure and transport properties of the descending limb (DL) of Henle of mammalian-type nephrons in Japanese quail, Coturnix coturnix. In the avian renal medulla, a prominent ring of collecting ducts and scattered thick limbs surrounds a core of capillaries and DLs. Epithelial cells in the upper DL (DLu) have abundant microvilli and shallow, tight junctions; cells in the lower DL are flat and have little interdigitation. Transepithelial voltage was zero when the DLu was perfused and bathed in isosmotic avian Ringer solution. The efflux coefficients (10(-7) cm2/s) for Na (31.7 +/- 2.3) and Cl (24.9 +/- 3.6) were not significantly different and were unaltered by ouabain (10(-4) M) (32.5 +/- 2.2). Diffusional water permeability measured by [3H]H2O was low (73.0 +/- 7.8, 10(-7) cm2/s). Volume flux was nearly zero and increased only slightly when an osmotic gradient was imposed. These results suggest the DLu is highly permeable to Na and Cl and virtually impermeable to water; thus NaCl extruded actively from the thick ascending limb may enter the DL unaccompanied by water. This countercurrent multiplication system by use of single-solute recycling and a transport cascade of graded hairpin turns may help establish an osmotic gradient along the medullary cone. Thus avian and mammalian renal countercurrent multiplication systems may differ.
Thromboxane A2 and prostaglandin endoperoxide analogue effects on porcine renal blood flow
Authors: Cirino M. , Morton H. , MacDonald C. , Hadden J. , Ford-Hutchinson A. W.
Published: December 2017

Thromboxane A2 (TxA2) has been implicated as a mediator of renal and cardiovascular diseases. However, the direct effects of TxA2 on the renal system have been difficult to study because of the instability of the agonist. In the present study injection of synthetic TxA2 directly into the renal artery of anesthetized pigs produced dose-related decreases in renal blood flow (RBF) from 101 +/- 11 to 12 +/- 3 ml/min at the highest dose (20 ng/kg). The reductions in RBF were similar to those produced by the stable prostaglandin endoperoxide analogue, U-44069, although TxA2 was three times more potent. Under these conditions there were no effects on either mean (MAP) or pulmonary arterial pressures (PAP), or the heart rate (HR). The maximal effects produced by TxA2 and U-44069 on RBF were reproducible and the response remained unchanged after pretreatment with either heparin or indomethacin. Systemically administered TxA2 (200 ng/kg iv) increased PAP from 20 +/- 1 to 34 +/- 3 mmHg and this effect was associated with modest increases in MAP and HR. Intravenous administration of the thromboxane receptor antagonist, L-655,240, inhibited the reductions in RBF produced by intrarenal TxA2 and U-44069 and attenuated the cardiopulmonary effects of TxA2 administered intravenously. The results demonstrate directly that TxA2 is a potent agent for decreasing RBF through interaction with a thromboxane receptor.
Acute cyclosporine-induced renal vasoconstriction: lack of effect of theophylline
Authors: Churchill P. C. , Rossi N. F. , Churchill M. C. , Bidani A. K. , McDonald F. D.
Published: December 2017

Both acute and chronic administration of cyclosporine A (CSA) lead to renal vasoconstriction, but the mechanism is not fully understood. The present studies were designed to explore the possible role of adenosine in acute CSA-induced renal vasoconstriction in rats. Six groups of anesthetized Sprague-Dawley rats were studied using standard clearance techniques: group 1 rats were controls; groups 2, 4, and 6 received CSA intravenously at 20, 30, and 40 mg.h-1.kg body wt-1, respectively; groups 3 and 5 were identical to groups 2 and 4 except that a priming injection of theophylline was given (56 mumol/kg body wt) and theophylline was included in the intravenous infusate (0.56 mumol.min-1.kg body wt-1). CSA produced acute and concentration-dependent reductions in renal plasma flow (left kidney) and in the clearances of p-aminohippuric acid and inulin (both kidneys). Except in group 6, these changes were observed in the absence of a decrease in arterial blood pressure, demonstrating that CSA produced an acute and concentration-dependent increase in renovascular resistance. Theophylline not only failed to block CSA-induced renal vasoconstriction, if anything, it potentiated it. Because theophylline is an adenosine receptor antagonist, these findings contradict the hypothesis that adenosine mediates acute CSA-induced renal vasoconstriction.
Origin of dopamine in the rat adrenal cortex
Authors: Buu N. T. , Lussier C.
Published: December 2017

The hypothesis that dopamine (DA) is involved in the control of aldosterone secretion is given some support by the finding of DA in the adrenal cortex of several species, but the source of this DA is not known. This study showed that the administration of L-dopa to intact rats or medullectomized rats caused a significant DA increase in the adrenal cortex. The DA increase in the cortex was more pronounced than in the medulla, coincident with higher L-dopa uptake by the cortical tissue. Tyrosine administration raised DA levels only in the medulla. Sympathectomy of the rat by 6-hydroxydopamine treatment did not affect DA basal levels in the cortex or the DA increase in this tissue after L-dopa injection. 3,4-Dihydroxyphenylacetic acid (DOPAC) is detectable in the adrenal cortex but not in the adrenal medulla, and DOPAC levels increased significantly after L-dopa, which indicates monoamine oxidase (MAO) activity within the adrenal cortex. Because 6-hydroxydopamine pretreatment did not alter DOPAC levels, cortical MAO may be located outside catecholaminergic neurons. The results established circulating L-dopa as a precursor for DA in the adrenal cortex of the rat. They also showed that tyrosine hydroxylase activity is absent from the adrenal cortex of this species.
Ouabain-induced lethal proximal tubule cell injury is prevented by glycine
Authors: Weinberg J. M. , Davis J. A. , Abarzua M. , Smith R. K. , Kunkel R.
Published: December 2017

Exposure to 1 mM ouabain for greater than 30 min caused lethal cell injury to isolated rabbit proximal tubules as measured by increased lactate dehydrogenase release. Addition of 2 mM glycine or glutathione to the incubation medium prevented this injury and a sharp fall of cell ATP that accompanied it. Glycine and glutathione did not alter rapid, early effects of ouabain to deplete cell K+ and inhibit respiration. Preservation of cellular glutathione was not required for protection. Glycine did not ameliorate ouabain-induced increases of cell water and did not prevent lethal cell injury associated with cell swelling produced by incubation in a high K+ concentration medium. In contrast, 100 mM mannitol, which at least partially ameliorated swelling in both ouabain and high-K+ medium, prevented lethal injury in high-K+ medium and decreased it in the presence of ouabain. The combination of glycine and mannitol completely prevented ouabain-induced lethal injury and cell water increases. These observations indicate that glycine, unlike mannitol, does not protect against primary volume-induced insults. Ouabain-induced lethal cell injury results from a process that includes both a volume component ameliorated by mannitol and a volume-independent component that is prevented by glycine and is closely associated with accelerated ATP depletion.
Effect of pH on Na(+)-dependent phosphate transport in renal outer cortical and outer medullary BBMV
Authors: Quamme G. A.
Published: December 2017

The influence of pH on sodium-phosphate cotransport was determined in brush-border membrane vesicles (BBMV) isolated from outer cortical and outer medullary tissue of porcine kidneys. Two transport systems are apparent in outer cortical brush-border vesicles, and one process is apparent in outer medullary vesicles at all pH values. The apparent maximum uptake rate (Vmax) of the low-affinity system in outer cortex vesicles decreased from 8.3 +/- 1.7 to 3.2 +/- 0.05 nmol.mg protein-1.min-1 with pH change of 8.0 to 6.0, and the high-affinity process changed from 1.3 +/- 0.2 to 0.1 +/- 0.01 nmol.mg protein-1.min-1. The respective affinity values (Km) also decreased 5.5 +/- 0.9 to 0.6 +/- 0.01 mM and 0.08 +/- 0.005 to 0.01 +/- 0.005 mM, respectively, with acidification. In outer medullary vesicles a decrease in pH diminished the apparent Km, 0.28 +/- 0.03 to 0.02 +/- 0.003 mM, and mean Vmax from 3.0 +/- 0.07 to 0.5 +/- 0.1 nmol.mg protein-1.min-1. The mean KNaD values were 22.1 +/- 4.2 mM in outer cortical vesicles (low-affinity system) and 58.7 +/- 7.2 mM in outer medullary vesicles (high-affinity system) and were not altered by pH, suggesting that H+ does not affect the sodium interactive site. The data suggest that the vesicles prepared from outer cortical and outer medullary tissue possess distinctive sodium-phosphate transporters that are sensitive to external H+ concentrations.
Morphological and functional comparisons of normal and hypertrophied kidneys of adult domestic fowl (Gallus gallus)
Authors: Gregg C. M. , Wideman R. F.
Published: December 2017

Similar to mammals, kidneys of domestic fowl undergo compensatory hypertrophy after loss of functional renal mass. Because this species continues to develop new nephrons for up to 12-wk posthatch, renal hyperplasia might play a significant role in compensatory growth. Either transient or permanent loss of approximately 60% of the right kidney was produced in 2- to 3-wk-old roosters by simple ureteral transection or by removing a 1-mm segment of ureter at the level of the ischiadic artery, respectively. In the latter (experimental) group, right anterior and medial divisions atrophied leaving only the posterior division intact. Spontaneous reanastomosis occurred in the former (reconnected) group, and all three divisions were present at death. Control birds were untouched as were the left kidneys of experimental and reconnected birds. At 40-50 wk, renal function was measured separately in right and left kidneys of all groups during five different infusion protocols. Compared with control kidneys, experimental kidneys had a 50-60% weight gain, and their glomerular size distribution profile was shifted to the right (larger glomeruli). Reconnected kidneys were not hypertrophied, and their profile was shifted to the left (smaller glomeruli). Neither group had significant formation of new nephrons. Once variations in kidney weight were taken into account, there were no differences between hypertrophied (experimental) and control kidneys in urine flow rate (UFR), glomerular filtration rate (GFR), paraaminohippuric acid (PAH) clearance, UFR/GFR, urine osmolality, urine/plasma osmolality, osmolal clearance, free water clearance, Na and K load, absolute Na and K excretion, and fractional Na and K excretion except as follows: 1) during infusion of isotonic mannitol-dextrose at 0.1 ml.min-1.kg body wt-1 experimental kidneys had a lower fractional excretion of K than control kidneys, and 2) during brisk osmotic diuresis (isotonic mannitol-dextrose at 0.4 ml.min-1.kg body wt-1) experimental kidneys had higher UFR and free water clearance and lower urine osmolality and urine/plasma osmolality than control kidneys. Reconnected kidneys differed from control kidneys in only 1 of 210 comparisons. Permanent loss of functional renal mass in young birds produces significant compensatory renal hypertrophy that is due to enlargement of existing nephrons rather than formation of new nephrons. Hypertrophied kidneys function like normal kidneys except under conditions of brisk osmotic diuresis.
HeLa cells express cAMP-inhibitable sodium-dependent phosphate uptake
Authors: Raymond J. R. , Middleton J. P. , Dennis V. W.
Published: December 2017

Receptor-mediated regulation of the sodium-phosphate symporter, and hence sodium-dependent phosphate uptake, typically relates to epithelial cells of renal origin. In this study we have characterized sodium-dependent phosphate uptake and aspects of its receptor-mediated regulation in the HeLa cell line, a cell line derived from a human epithelioid carcinoma. Phosphate uptake (greater than 90% sodium dependent; Vmax = 4.02 +/- 0.24 nmol.mg and Km = 0.11 +/- 0.02 mM phosphate at 140 mM sodium) was kinetically similar to that observed in opossum kidney cells. Incubation with vasoactive intestinal peptide (VIP) resulted in a dose-dependent (50% maximal dose of 8.8 +/- 3.6 nM) approximately fivefold increase in basal adenosine 3',5'-cyclic monophosphate (cAMP) levels (basal = 14.6 +/- 1.7 pmol.mg protein-1.15 min-1; VIP stimulated = 72.7 +/- 13.2 pmol.mg protein-1.15 min-1), as well as a dose-dependent maximal 32.6 +/- 5.5% decrease in sodium-dependent phosphate uptake (50% maximal decrease of 46.2 +/- 21.2 nM). The VIP-induced decrease in phosphate uptake was due to decrease in maximal transport (VmaxVIP = 2.78 +/- 0.16 nmol.mg protein-1.3 min-1) and not to a change in the affinity of the transporter for phosphate (KmVIP = 0.11 +/- 0.01 mM phosphate). Preincubation of HeLa cells with forskolin and cholera toxin, which stimulate adenylate cyclase, resulted in dose-dependent decreases in sodium-dependent phosphate uptake. Incubation with 8-bromo-cAMP and dibutyryl cAMP, permeant analogues of cAMP, similarly resulted in a dose-dependent decrease in sodium-dependent phosphate uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
Brain natriuretic peptide: interaction with renal ANP system
Authors: Gunning M. , Ballermann B. J. , Silva P. , Brenner B. M. , Zeidel M. L.
Published: December 2017

Brain natriuretic peptide (BNP) has recently been found in porcine brain and has been shown to cause diuresis and natriuresis when injected in rats, effects similar to those caused by atrial natriuretic peptide (ANP). BNP is also synthesized in the cardiac atria and circulates in plasma. The amino acid sequence of the peptide resembles that of ANP particularly closely within the ring structure of the peptide. We examined the potential role of BNP in modulating renal function by assessing its ability to mimic the effects of ANP on rat glomeruli and in rabbit inner medullary collecting duct cells (IMCD). BNP bound with high affinity to glomeruli (Kd approximately 900 pM) and IMCD cells (Kd approximately 500 pM). In IMCD cells, BNP stimulated particulate guanylate cyclase (approximately 3-fold at maximum ligand concentration) and inhibited conductive 22Na+ uptake by 50% at concentrations at which ANP is also effective. In rat glomeruli, BNP bound with high affinity to the low-molecular-weight receptors but with lesser affinity to the higher-molecular-weight guanylate cyclase-linked receptors (Kd approximately 50 nM). In addition, the guanosine 3',5'-cyclic monophosphate accumulation response was less impressive in glomeruli than the guanylate cyclase response in IMCD tissue. Thus we conclude that BNP is of only slightly reduced affinity and potency for the ANP receptors in the kidney and probably acts through these receptors to exert its physiological effects.
Influence of acute and chronic respiratory alkalosis on preexisting chronic metabolic alkalosis
Authors: Madias N. E. , Cohen J. J. , Adrogue H. J.
Published: December 2017

The severity of the alkalemia produced by a reduction in arterial carbon dioxide tension (PaCO2) in normal humans and animals is ameliorated by buffer and renal responses that diminish the levels of plasma bicarbonate concentration ([HCO3-]p). These adjustments have even greater potential importance in preventing extreme degrees of alkalemia when hypocapnia occurs in the presence of an initially elevated [HCO3-]p (mixed respiratory and metabolic alkalosis). The aim of the present study was to characterize the acute (approximately 3 h) and chronic (5 days) acid-base effects of respiratory alkalosis when superimposed on chronic metabolic alkalosis. Ten dogs were made alkalotic by the repeated administration of ethacrynic acid and the provision of a chloride-restricted diet. Hypocapnia (delta PaCO2 = 10 mmHg) was then superimposed by exposing the animals to 11% O2 in an environmental chamber. A large fall in [HCO3-]p occurred in the acute hypocapnic phase that was further augmented in the chronic phase; the corresponding delta [HCO3-]p/delta PaCO2 slopes were 0.43 and 0.71 meq.l-1.mmHg-1, respectively, values substantially larger than those previously reported for hypocapnia in normals as well as in animals with preexisting HCl acidosis. Hyperlactatemia was responsible, on average, for 43% of the decrement in [HCO3-]p during acute hypocapnia but for only 20% of the delta [HCO3-]p during the chronic phase of the study. The striking decrement in [HCO3-]p observed in response to the chronic reduction in PaCO2 was sufficient not only to prevent the development of extreme alkalemia but also to offset entirely the effect of hypocapnia on plasma [H+].
Hormonal interactions with the proximal Na(+)-H+ exchanger
Authors: Gesek F. A. , Schoolwerth A. C.
Published: December 2017

Various types of catecholamine and peptide hormone receptors have been localized to the renal cortex, with the majority of these binding sites located on the proximal tubule. Both subtypes of alpha-adrenergic receptors, angiotensin II (ANG II), parathyroid hormone (PTH), and dopamine (DA) DA-1 receptors have all demonstrated binding sites on this nephron segment. One- to two-thirds of Na+ transport in the proximal nephron is proposed to be mediated by a Na(+)-H+ exchanger. Each of these hormones has been shown to alter Na(+)-H+ exchange activity. The purpose of this study was to examine the interactions of these various hormones on proximal nephron Na(+)-H+ exchange at both physiological and pharmacological concentrations. Na(+)-H+ exchange activity was determined in isolated rat proximal segments by assessing the uptake of 22Na+ that was suppressible by the Na(+)-H+ exchange inhibitor, ethylisopropylamiloride (EIPA). Time course studies indicated that a 1-min preincubation with the hormones followed by a 1-min exposure to 22Na+ was necessary to achieve a steady-state EIPA-suppressible 22Na+ uptake. Selective alpha-adrenergic agonists produced a maximum stimulation of 22Na+ uptake at approximately 10(-6) M final concentration (less than or equal to 192% above the control level of uptake); ANG II produced a maximum increase at 10(-12) M (an 82% increase above the control level). In contrast, PTH and DA inhibited 22Na+ uptake most effectively at 10(-8) M and 10(-6) M, respectively. When submaximal (10(-9) M) concentrations of alpha-agonists were incubated in combination with ANG II, a synergistic effect was observed only with selective alpha 2-agonists.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of apical membrane Cl(-)-formate exchange on cell volume in rabbit proximal tubule
Authors: Schild L. , Aronson P. S. , Giebisch G.
Published: December 2017

We used real-time recordings of cell volume changes to test for the role of the Cl(-)-formate exchanger in mediating NaCl entry across the apical membrane of rabbit proximal tubule cells. In the absence of extracellular Cl-, 0.5 and 5 mM formate in the tubule lumen induced an increase in cell volume of 1 and 9%, respectively. Formate-induced cell swelling was reduced by alkalinizing the tubule lumen or by addition of luminal amiloride (2 mM), indicating that the increase in cell volume results from the intracellular accumulation of Na-formate via nonionic diffusion of formic acid in parallel with Na(+)-H+ exchange. The cell volume increase induced by 0.5 mM formate was potentiated (from 1 to 4%) by Cl-, as expected for a formate-mediated stimulation of NaCl uptake via parallel Cl(-)-formate exchange and Na(+)-H+ exchange across the apical membrane. By contrast, the cell volume increase induced by 5 mM formate was attenuated (from 9 to 4%) by Cl-. The attenuating effect of Cl- on formate-induced cell swelling required the operation of the apical membrane Cl(-)-formate exchanger. The effect of 1:1 Cl(-)-formate exchange to attenuate formate-induced cell swelling can be explained if the cell possesses a volume-activated anion exit pathway, most likely at the basolateral cell membrane, that is capable of mediating the efflux of Cl- but not formate from the cell.
MPP+ is transported by the TEA(+)-H+ exchanger of renal brush-border membrane vesicles
Authors: Lazaruk K. D. , Wright S. H.
Published: December 2017

Rabbit renal brush-border membrane vesicles (BBMV) were used to study the transport of the cationic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). An outwardly directed H(+)-gradient stimulated MPP+ uptake and led to the development of an active accumulation of MPP+ within the vesicles. H(+)-gradient driven MPP+ transport was saturable, with a maximal transport rate of 3 nmol.mg-1.min-1 and an apparent Michaelis constant (Kt) of 8 microM. MPP+ and tetraethylammonium (TEA) behaved as competitive inhibitors of one another's transport in renal BBMV, suggesting the presence of a common transport pathway for these organic cations. At an ambient pH of 7.5, preloading BBMV with MPP+ failed to stimulate TEA uptake, although trans TEA did stimulate MPP+ uptake. Increasing ambient pH to 8.5 (i.e., reducing competition between H+ and these organic cations for a common transport pathway) led to a clear reciprocal trans stimulation of TEA and MPP+ fluxes. With an equilibrium-shift protocol, a trans concentration of MPP+ energized uphill transport of TEA. We conclude that MPP+ and TEA share a common organic cation-H+ exchange pathway in the renal brush border, although turnover of an MPP(+)-loaded exchanger is slow compared with that for a TEA or H(+)-loaded exchanger.
[Ca2+]i rises via G protein during regulatory volume decrease in rabbit proximal tubule cells
Authors: Suzuki M. , Kawahara K. , Ogawa A. , Morita T. , Kawaguchi Y. , Kurihara S. , Sakai O.
Published: December 2017

Although animal cells swell in hypotonic medium, their volume is subsequently regulated by a net loss of KCl via Ca2(+)-dependent channels. A rise in intracellular free calcium ([Ca2+]i) thus appears to be an initial event in the adaptation of external tonicity, although details of this mechanism are not known. To investigate cell volume regulation, we measured [Ca2+]i (by use of fura-2) and cell diameters in single cells of cultured renal proximal convoluted tubule. We found that a rapid rise in [Ca2+]i occurred after cells were exposed to hypotonic solution (250 mosM) from 95.8 +/- 3.8 to 468.2 +/- 24 nM (n = 16). The rise in [Ca2+]i was not observed in cells exposed to Ca2(+)-free medium, and exposure to isotonic high-K or low-Na medium did not elicit a rise in [Ca2+]i, suggesting that this rise was a result of Ca2+ influx and not via voltage-dependent Ca2+ influx or decrease of Ca2+ efflux via Na(+)-Ca2+ pump. Pretreatment of cells with pertussis toxin dose dependently blocked the rise in [Ca2+]i. The hypotonic solution enhanced accumulations of inositol tris- and tetra-phosphate after a 1-min exposure. Studies that measured cell diameters suggest that recovery of cell volume may include the rise in [Ca2+]i. These data suggest that the regulatory volume decrease of proximal tubule cells involves a pertussis toxin-sensitive guanine nucleotide binding protein-operated Ca2+ influx.
Volume regulation following Na+ pump inhibition in CCT principal cells: apical K+ loss
Authors: Strange K.
Published: December 2017

Ouabain caused rabbit cortical collecting tubule (CCT) principal cells to swell 67%. Swollen cells downregulated their volume at a rate of 4%/min to a new volume 16% below control. A qualitatively similar pattern of swelling and volume regulation was observed with peritubular addition of 2.0 microM prostaglandin E2 (PGE2), a putative endogenous Na+ pump inhibitor. Regulatory volume decrease (RVD) in ouabain-swollen cells was inhibited 50-70% by bilateral addition of 2.0 mM Ba2+ or 5.0 mM TEA+. Peritubular TEA+ had no effect on RVD. Luminal addition of 5.0 mM TEA+ or 0.2 mM quinidine inhibited RVD 50-60%, suggesting involvement of an apical K+ channel. This channel appeared to be distinct from the resting apical K+ conductance. Replacement of cellular K+ with Rb+, which is commonly used as a tracer of K+ secretion in the CCT, had little effect on the rate and magnitude of ouabain swelling but inhibited RVD 50-60%. A 10-fold elevation of luminal K+ before ouabain or after completion of RVD caused principal cells to swell 10% and 31%, respectively. In control cells, this K(+)-induced swelling was unaffected by the presence of 1.0 mM quinidine in the perfusate and could be mimicked by elevation of Rb+ instead of K+ concentration. The magnitude of swelling in volume-regulated principal cells, however, was reduced 50-60% by the presence of luminal quinidine or by luminal addition of Rb+ instead of K+. The putative apical RVD K+ channel may be similar to high-conductance K+ channels described in principal cell patch-clamp studies from other laboratories.
Volume homeostasis in calves with artificial atria and ventricles
Authors: Westenfelder C. , Birch F. M. , Baranowski R. L. , Riebman J. B. , Olsen D. B. , Burns G. L. , Kablitz C.
Published: December 2017

We examined whether replacement of cardiac atria and ventricles with total artificial hearts (TAH), a procedure that removes cardiac nerves and all sources of atrial natriuretic factor (ANF), would cause alterations in volume homeostasis in awake calves. Preoperatively, extracted plasma immunoreactive (ir)ANF levels were 13.3 +/- 0.6 and remained postoperatively at 10.5 +/- 0.4 pg/ml (P less than 0.01). TAH implantation caused systemic and pulmonary hypertension (P less than 0.01), salt retention, edema, and significant elevations of plasma renin, aldosterone, and arginine vasopressin. In intact calves rapid infusion of 6 liters of normal saline raised irANF levels to 73.7 +/- 6.5 pg/ml (P less than 0.01) and elicited a large natriuresis and diuresis. No such response to 6 liters of normal saline was obtained after calves had recovered from TAH implantation. Reduction of cardiac output (CO) by 50% caused further salt retention and no change in irANF levels. Elevation of CO back to and 33% above base line produced only a diuresis, whereas salt retention persisted and irANF levels remained unchanged. The same maneuvers elicited in surgical control calves (artificial ventricles only, largely intact atria) a significant increase in irANF levels and a diuresis and natriuresis. In conclusion, alterations in volume homeostasis observed after TAH implantation seem to be the consequence of at least two pathophysiological mechanisms: 1) functional ANF "deficiency," characterized by apparently unregulated ANF secretion from noncardiac sites, and 2) cardiac denervation.
Role of atrial peptide in the acute natriuretic response to uninephrectomy
Authors: Valentin J. P. , Ribstein J. , Pussard E. , Mimran A.
Published: December 2017

Unilateral nephrectomy (UNX) is associated with an immediate natriuretic response of the remaining kidney. The role of atrial natriuretic peptide (ANP), as assessed by right atrial appendectomy (APX), was investigated in euvolemic anaesthetized rats. In sham APX rats, UNX resulted in a twofold increase in urinary sodium and potassium excretion (1.03 +/- 0.11 to 2.08 +/- 0.17 and 1.39 +/- 0.05 to 2.26 +/- 0.08 mueq/min, respectively) and a doubling of urinary excretion of guanosine 3',5'-cyclic monophosphate (cGMP). No significant change in glomerular filtration rate, renal plasma flow, and lithium clearance occurred in response to UNX. APX totally prevented the UNX-induced natriuresis and diuresis as well as the rise in urinary cGMP. Post-UNX plasma concentration of ANP was higher in sham-operated compared with APX rats (45 +/- 9 vs. 20 +/- 2 fmol/ml). In sham APX rats, UNX was associated with a transient (less than 15 min) rise in arterial pressure; in APX rats, this immediate increase in arterial pressure was of similar magnitude but of longer (greater than 30 min) duration. The observed stimulation of ANP release after UNX and the blunting of the natriuretic response to UNX by APX suggest that ANP may be an important mediator of the renal response to contralateral renal ablation.
K+ alters cytochrome P-450-dependent arachidonate metabolism by rabbit renomedullary cells
Authors: Carroll M. A. , Louzan M. , McGiff J. C.
Published: December 2017

We studied the effects of K+ on cytochrome P-450-dependent arachidonic acid (P450-AA) metabolism by cells isolated from the rabbit medullary thick ascending limb of Henle's loop (MTAL) by varying K+ from 0 to 7.5 mM in the incubating medium because of the known effects of K+ on AA metabolism. Rabbit MTAL cells convert AA to metabolites that segregate into two peaks (P1 and P2) on reverse-phase high-performance liquid chromatography; P1 contains vasodilator material and P2 an inhibitor(s) of Na(+)-K(+)-ATPase activity. Formation of P450-AA metabolites by MTAL was enhanced by reducing external K+ (P less than 0.01) and was not affected by changes in external Cl- but was dependent on the presence of intact MTAL cells, suggesting that P450-AA metabolism was related to altering ion fluxes and/or cell volume changes. The effects of altered external K+ on MTAL P450-AA metabolism could be nullified by increasing K+ intake before killing the rabbits. Evidence for the absence of a direct effect of zero K+ on Na(+)-K(+)-ATPase was provided by the demonstration that ouabain failed to affect AA metabolism in MTAL cells. We conclude that P450-AA metabolism by MTAL cells can be influenced either directly by altering external K+ in the incubate or indirectly by changing dietary K+ before killing the rabbits. Furthermore, MTAL P450-AA metabolism was independent of changes in external Cl- and Na(+)-K(+)-ATPase activity.