bluuebunny/crossref_metadata_2025 huggingface dataset:
Atriopeptin III alters renal medullary hemodynamics and the pressure-diuresis response in rats
Authors: Takezawa K. , Cowley A. W. , Skelton M. , Roman R. J.
Published: December 2017

The effects of atriopeptin III on the renal response to changes in renal perfusion pressure (RPP) were examined in uninephrectomized and adrenalectomized rats. Neural influences on the kidney were eliminated by renal denervation. Plasma levels of antidiuretic hormone (ADH), angiotensin II, aldosterone, corticosterone, and norepinephrine were controlled by intravenous infusion. Infusion of atriopeptin III at a dose of 30 or 100 ng X kg-1 X min-1 increased plasma levels of atrial natriuretic peptide from 101 +/- 8 pg/ml to 424 +/- 16 and 2,553 +/- 308 pg/ml, respectively. In control rats, increasing RPP in two steps from 100 to 125 to 150 mmHg produced sixfold increases in sodium and water excretion. The slopes of the relationships between fractional sodium and water excretion and RPP were enhanced by approximately 10, 20, and 40% in the rats infused with the 30, 100, and 500 ng X kg-1 X min-1 dose of atriopeptin III. Renal blood flow and glomerular filtration rate were not significantly different in vehicle- and atriopeptin III-infused rats at any RPP studied. Papillary blood flow measured with a laser-Doppler flowmeter increased 15% within the first 5 min of infusion of atriopeptin III at a dose of 100 ng X kg-1 X min-1. Cortical blood flow was not significantly altered. The rise in papillary blood flow during atriopeptin III infusion, however, may be a consequence and not the cause of the natriuresis and diuresis, since urine flow increased before significant changes in papillary blood flow were detected. These studies suggest that atrial natriuretic factor could influence the long-term control of arterial pressure by altering renal medullary hemodynamics and promoting the elimination of sodium and water. The plasma levels of atrial natriuretic peptide needed to alter the pressure-natriuresis relationship, however, may exceed levels that can be attained in vivo with endogenous release.
Effects of PDGF on inositol phosphates, Ca2+, and contraction of mesangial cells
Authors: Mene P. , Abboud H. E. , Dubyak G. R. , Scarpa A. , Dunn M. J.
Published: December 2017

Platelet-derived growth factor (PDGF) is a potent mitogen and vasoactive polypeptide for aortic smooth muscle. Because contractile glomerular mesangial cells synthesize a PDGF-like molecule and may respond to PDGF released by infiltrating cells at the site of glomerular inflammation, we studied the effects of exogenous, highly purified PDGF on 1) contraction of cultured rat mesangial cells and 2) membrane phosphoinositide turnover and cytosolic free calcium ([Ca2+]i), as putative mechanisms of membrane signal transduction. PDGF, 10(-11) and 10(-10) M, contracted 56.1 +/- 5.2 and 72.9 +/- 6.4% of the cells, respectively, with an average decrease of cross-sectional area of 22.0 +/- 2.6 and 28.1 +/- 2.7% of basal, as assessed by image-analysis microscopy. PDGF also rapidly increased total water-soluble inositol phosphates, measured after anion-exchange chromatography on perchloric acid-extracted cells, and simultaneously raised [Ca2+]i, measured by the fluorescent intracellular probe fura-2, from basal levels of 83.1 +/- 6.8 to a peak of 229.4 +/- 20.0 nM. We conclude that PDGF stimulates contraction of rat mesangial cells via a phospholipase C-dependent pathway, with potential relevance to the control of glomerular hemodynamics and mesangial proliferation in immune-mediated glomerular disease.
Characteristics of H+ current transients induced by adverse H+ gradient pulses in toad bladder
Authors: Nero A. C. , Schwartz J. H. , Furtado M. R.
Published: December 2017

Acidification in the toad bladder occurs as a result of electrogenic H+ secretion (JH). When a pH gradient is applied in a stepwise fashion in the absence of exogenous CO2, JH decreases linearly with the mucosal (M) solution pH and is null when pHm is approximately 4.5. When pHm is returned to initial values (7.4) in a stepwise fashion, JH increases linearly with pHm. However, on this return, higher values of JH are initially obtained. To investigate this hysteresis, hemibladders mounted in chambers were used to measure the change in the H+ current before and after acid pulses were applied to the mucosal solution. In the absence of exogenous CO2, the application of graded acid pulses to mucosa for 1, 2, 4, and 8 min resulted in a graded decrease in JH. The restoration of pHm to 7.4 was followed by an immediate transient overshoot of reversed short-circuit current (Irsc), which was related to the time of exposure and the magnitude of the acid pulse. The longer the acid pulse or the larger the pulse, the greater the Irsc overshoot. The addition of protonophores, dinitrophenol, or salicylate, into the mucosal solution enhanced this overshoot. Similar Irsc overshoots could be obtained with the application of pulses of adverse electrical gradients. Introduction of exogenous CO2 into the system (3%) completely inhibited the overshoot in JH after an acid pulse. In conclusion, when pHm is decreased JH is reduced and the cell pH presumably decreases because of continued exit of alkali at the serosal side of the cell and entry of H+ from the mucosal solution. The decrease in cell pH then triggers the pump to produce a sharp overshoot in JH when pHm returns to 7.4.
Prostaglandins and the urinary concentrating defect in potassium-depleted rabbits
Authors: Raymond K. H. , Lifschitz M. D. , McKinney T. D.
Published: December 2017

Urinary prostaglandin E (UPGE) excretion increased significantly after 1 and 2 wk of potassium depletion (KD) in female New Zealand White rabbits on ad libitum water intake [UPGE control, 21.3 +/- 4.6 ng PGE/mg creatinine; 1 wk KD, 40.4 +/- 6.1 ng PGE/mg creatinine (P less than 0.01); 2 wk KD, 31.9 +/- 14.9 ng PGE/mg creatinine (P less than 0.05)]. In vivo prostaglandin inhibition with indomethacin or meclofenamate significantly increased urinary osmolality after 12 h of dehydration and exogenous vasopressin (1.25 U) from 794 +/- 59 to 1,163 +/- 113 mosmol/kgH2O (P less than 0.01). In vitro prostaglandin inhibition with indomethacin or meclofenamate corrected the antidiuretic hormone (ADH) unresponsiveness of isolated perfused cortical collecting tubules (CCTs) from KD rabbits. Furthermore, preincubation with pertussis toxin, an agent that inactivates the guanine nucleotide inhibitory (Ni) subunit of adenylate cyclase, normalized the ADH response of KD CCTs, suggesting that prostaglandins may attenuate ADH action on the CCT through activation of Ni and contribute to the urinary concentrating defect associated with KD.
Plasma potassium and diurnal cyclic potassium excretion in the rat
Authors: Rabinowitz L. , Berlin R. , Yamauchi H.
Published: December 2017

The relation of the plasma potassium concentration to the daily cyclic variation in potassium excretion was examined in undisturbed, unanesthetized male Sprague-Dawley rats maintained on a liquid diet in a 12-h light-dark environment. Potassium excretion increased from a light-phase minimum of 16 mu eq/h to a peak of 256 mu eq/h 3 h after the beginning of the dark phase. Plasma potassium concentration in arterial blood, sampled in rats at 90-min intervals during these changes in potassium excretion, showed no significant change and was in the range 4.50-4.99 meq/liter. In adrenalectomized rats receiving aldosterone and dexamethasone at constant basal rates by implanted pumps, the daily cycle of potassium excretion was the same as in the intact rats, and plasma potassium was not significantly different when measured at the time of minimum and maximum rates of potassium excretion (4.79 +/- 0.42 vs 5.16 +/- 0.47 meq/liter, mean +/- SD). These results indicate that plasma potassium concentration is not the efferent factor controlling diurnal cyclic changes in potassium excretion in adrenal intact rats and may not be the only significant factor in adrenalectomized-steroid replaced rats.
Glomerular ANF receptor regulation during changes in sodium and water metabolism
Authors: Gauquelin G. , Garcia R. , Carrier F. , Cantin M. , Gutkowska J. , Thibault G. , Schiffrin E. L.
Published: December 2017

The concentration of atrial natriuretic factor (ANF) in atria and plasma was investigated in relation to the regulation of renal glomerular ANF receptors in the rat during changes in water and sodium intake. A decrease in plasma immunoreactive ANF (IR-ANF) was observed after 4 days of water deprivation or after 1 wk on a low-sodium diet, whereas animals offered 1% NaCl in their drinking water had elevated plasma ANF values. Atrial IR-ANF was lower in water-deprived and higher in sodium-restricted rats than in their respective controls. A low-sodium intake or water deprivation increased the density of glomerular ANF receptors, whereas the inverse occurred with a high-salt consumption. It is concluded that an inverse correlation exists between ANF plasma concentration and renal glomerular ANF receptor sites.
Basal and hormone-activated calcium absorption in mouse renal thick ascending limbs
Authors: Friedman P. A.
Published: December 2017

These studies examined transepithelial routes of basal and hormone-activated calcium absorption in thick ascending limbs of Henle's loop perfused in vitro. Single cortical (cTAL) or medullary (mTAL) thick ascending limbs were dissected from kidneys of normal mice. Tubules were perfused at 37 degrees C at pH 7.4 in bicarbonate-buffered media for cTALs and in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered solutions for mTALs. Calcium was determined by electrothermal atomic absorption spectrophotometry. External driving forces for calcium were eliminated by perfusing and bathing tubules with symmetric solutions containing identical calcium concentrations and by abolishing the transepithelial voltage (VT), by adding furosemide or bumetanide to the luminal perfusate. Basal calcium absorption averaged 60 X 10(-12) mol.s-1.cm-2 in cTAL. After addition of 1 U/ml parathyroid hormone (PTH)-(1–34), net calcium absorption increased to 162 X 10(-12) mol.s-1.cm-2 (P less than 0.05) with no change in VT. Similarly, addition of 10(-3) M dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) to external bathing solutions increased net calcium absorption to 201 from 70 X 10(-12) mol.s-1.cm-2 in control conditions (P less than 0.025). These results demonstrate that PTH, acting at least in part through cAMP, activates a cellular pathway for calcium absorption in cTAL. In segments of mTAL, calcium absorption was strictly voltage dependent: when VT was abolished, net calcium absorption fell to values indistinguishable from zero and was not altered in the presence of dibutyryl cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)
Transition of permeability properties along the descending limb of long-loop nephron
Authors: Imai M. , Taniguchi J. , Yoshitomi K.
Published: December 2017

The isolated segments of the hamster descending limb of the long-loop nephron (LDL) were perfused in vitro to demonstrate the axial heterogeneity with respect to permeability properties. When a NaCl gradient from the lumen to bath was present, the lumen-negative diffusion voltage (VD) was generated in the upper portion (LDLU). When the VD was measured stepwise along the axis of tubules, the magnitude of the VD decreased in the portion within 0.5 mm before the border between the outer and inner medulla in most cases, indicating that a gradual functional transition to the lower portion (LDLL) occurs along the descending limb. The lumen-to-bath flux coefficients (K1----b) for Na+ were 14.3 +/- 3.7 X 10(-7) and 2.4 +/- 0.8 X 10(-7) cm2/s in the LDLU and LDLL, respectively. The K1----b for urea were 1.7 +/- 0.6 X 10(-7) and 7.9 +/- 4.1 X 10(-7) cm2/s, respectively. The LDLL was highly permeable to water, with osmotic permeability coefficient being 1,693 +/- 517 X 10(-9) cm2.s-1.atm-1. The reflection coefficients for NaCl and urea were not different from unity. From these observations, we conclude that the functional transition occurs along the LDL from the segment with a high Na+ permeability to that with a low Na+ permeability.
Transport of tetraethylammonium by a kidney epithelial cell line (LLC-PK1)
Authors: Fauth C. , Rossier B. , Roch-Ramel F.
Published: December 2017

The aim of this study was to test the hypothesis that the intrarenal renin-angiotensin system (RAS) modulates glomerular angiotensin II (ANG II) receptors. In one protocol ANG II receptors were measured 7 days after unilateral denervation of the left kidney in rats. There were 50% more receptors in the glomeruli from denervated compared with innervated kidneys (right, 1,037 +/- 108 vs. left, 1,556 +/- 143 fmol/mg; P less than 0.01), which was associated with a 63% reduction (P less than 0.01) in left renal vein renin. The differences in ANG II receptors between the left and right kidneys were no longer present when angiotensin-converting enzyme was inhibited with enalapril or when pharmacological amounts of ANG II (50 ng/min) were infused. In a second protocol, renal cortical renin content was raised in the left kidney by placing a 0.20-mm clip on the left renal artery (two-kidney, one-clip Goldblatt model). At 7 days, glomerular ANG II receptors were reduced by 72.3% in the clipped compared with the contralateral kidneys (right, 1,232 +/- 105 vs. left, 341 +/- 170 fmol/mg; P less than 0.01). The differences in ANG II receptors were no longer present after enalapril treatment. Pharmacological maneuvers that either blocked ANG II formation or increased circulating ANG II resulted in an equal number of ANG II receptors in the right and left kidneys. The data indicate that the intrarenal RAS modulates the density of glomerular ANG II receptors and is a more important receptor modulator than plasma ANG II.
Effect of a converting-enzyme inhibitor on vasa recta blood flow in rat kidney
Authors: Hansell P. , Sjoquist M. , Ulfendahl H. R.
Published: December 2017

In young anesthetized Munich-Wistar rats, red cell flux (Qrbc) was measured in the vasa recta of the exposed renal papilla by means of fluorescently labeled erythrocytes. To study the vasoreactivity of the juxtamedullary vasculature and its sensitivity to converting-enzyme inhibition, measurements of Qrbc were made before and after continuous intravenous infusion of the angiotensin I converting-enzyme inhibitor captopril (3 mg.h-1.kg body wt-1). A time control group that received vehicle alone was studied in parallel. Captopril acts as a vasodilator and reduces systemic arterial pressure. Captopril treatment increased Qrbc by 40 +/- 4% (n = 9, P less than 0.001) and decreased blood pressure by 9% (P less than 0.001). In the time control group no statistically significant change occurred in either Qrbc (+6 +/- 8%, n = 10) or blood pressure (-1%). Urine samples were taken from the papillary tip. In neither of the groups did the urine osmolality show a statistically significant change. In the time control group the values before and after intravenous infusion were 1,006 +/- 61 and 1,091 +/- 70 mosmol/kg H2O, respectively, and in the captopril-treated animals the corresponding values were 1,150 +/- 85 and 1,210 +/- 60 mosmol/kg H2O, respectively. These results confirm the suggestion that there is high vasoreactivity in the juxtamedullary vasculature and that this region is sensitive to inhibition of angiotensin I-converting enzyme, the latter sensitivity implying that angiotensin II plays a role in the regulation of juxtamedullary vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of rapid sodium load on circulating atrial natriuretic polypeptide
Authors: Nishida Y. , Miyata A. , Morita H. , Uemura N. , Kangawa K. , Matsuo H. , Hosomi H.
Published: December 2017

The hypothesis that an increase in plasma sodium concentration (PNa) causes an increase in circulating atrial natriuretic polypeptide (ANP) was examined in conscious dogs. NaCl solution in small volume (0.3 ml/kg body wt) and at high concentration (20%) was injected intravenously within 2 s to rapidly increase PNa. PNa rapidly increased to 5.1 +/- 0.3 meq/l. Urinary excretion of sodium and water increased to 4.1 and 2.5 times the control levels, respectively. Plasma vasopressin level increased to 3.7 times the control level. Plasma ANP level (PANP) did not change significantly. PANP corrected for sodium-induced hemodilution did not change either. On a different day, a double amount of sodium (0.6 ml/kg body wt of 20% NaCl solution) was intravenously injected into the dogs. PNa increased by 7.3 +/- 0.4 meq/l, which was significantly more than the increase after the 0.3 ml/kg injection. PANP with or without correction for hemodilution again did not change. These results indicate that a rapid increase in PNa within the physiological range does not cause elevation of circulating ANP. This suggests that ANP does not contribute to the regulation of plasma sodium concentration.
Evaluation of prostaglandins as mediators of tubuloglomerular feedback
Authors: Franco M. , Bell P. D. , Navar L. G.
Published: December 2017

Orthograde and retrograde microperfusion experiments were conducted in Sprague-Dawley rats to evaluate the participation of vasoconstrictive eicosanoids as mediators of tubuloglomerular feedback (TGF) signals. Retrograde perfusion with 160 microM arachidonic acid (AA) added to a hypotonic solution enhanced the stop-flow pressure (SFP) feedback responses compared with those obtained with the control hypotonic solution (delta SFP, 1.6 +/- 0.4 vs. 10.1 +/- 0.7 mmHg with AA). Blockade of thromboxane A2 (TxA2) with the receptor blocker EP 092 or the synthesis inhibitor UK 38485 did not alter the magnitude of the SFP feedback responses obtained with an isotonic solution. Similarly, nordihydroguaiaretic acid, a lipoxygenase inhibitor, did not alter maximal SFP feedback responses. Although indomethacin (5 mM) did induce attenuated SFP feedback responses (delta SFP, 9.5 +/- 0.7 vs. 0.5 +/- 0.4 mmHg with indomethacin), normal feedback responses were restored within 15-90 s after cessation of indomethacin perfusion. Additionally, SFP feedback responses were not inhibited with 5 mM piroxicam, a different cyclooxygenase inhibitor. These data fail to support a role for either TxA2 or lipoxygenase end products as mediators of TGF signals. The rapid restoration of feedback responses after indomethacin exposure and the lack of blockade with piroxicam suggest that transmission of feedback signals is not dependent on cyclooxygenase products.
Localization and secretion of newly synthesized and stored renin: two compartments and secretory mechanisms
Authors: Kawamura M. , Parmentier M. , Inagami T.
Published: December 2017

Intracellular pathways of renin secretion were examined by use of rat renal cortical slices. Renin was labeled with [35S]methionine by incubating the cortical slices for 2 h. The labeled immunoprecipitable renin was found in microsomal fraction (F1) but not in the renin granule fraction (F2). The newly synthesized and radiolabeled renin was secreted from the incubated slices into the medium. The rate of secretion of the labeled renin activity was not increased by 10(-6) M isoproterenol, whereas secretion of total renin activity was markedly stimulated. The isoelectric focusing patterns of renin in F1 and F2 were compared with those secreted with or without isoproterenol. The pattern of F1 was similar to that secreted in the medium without stimulation. These studies suggest that a constitutive pathway exists for renin secretion from the kidney and that the constitutive (nonstimulable) pathway is responsible for the secretion of newly synthesized renin and that it is not stimulated by a beta-adrenergic mechanism.
Changes in cytochrome oxidation in outer and inner stripes of outer medulla
Authors: Atkins J. L. , Lankford S. P.
Published: December 2017

To examine regional cytochrome oxidation in the outer medulla, we developed fiber optic probes that allowed us to obtain localized reflectance measurements from the outer and inner stripes of the outer medulla. We measured directional changes in cytochrome oxidation in these two regions. In the outer stripe furosemide surprisingly caused a significant decrease in cytochrome oxidation. The decrease occurred concomitantly with a fall in outer medullary blood flow as measured by laser-Doppler flowmetry. Saralasin, an antagonist of angiotensin II caused a significant increase in cytochrome oxidation in the outer stripe. In the inner stripe furosemide tended to increase cytochrome oxidation, and saralasin had no effect. These results indicate that the two regions of the outer medulla may be affected differently by the same agent. They suggest that cytochrome oxidation in the outer stripe is predominantly influenced by outer medullary blood flow, whereas the inner stripe is predominantly influenced by the rate of oxygen consumption. The advantages and limitations of this methodology are discussed.
Control of kidney size by sex hormones: possible involvement of glucosylceramide
Authors: Shukla A. , Shukla G. S. , Radin N. S.
Published: December 2017

Because androgenic hormones produce an increase in kidney size and the production of kidney glycosphingolipids and because the level of tissue glucosylceramide (GlcCer) has been implicated as a modulator of organ size, we measured the activities of two enzymes in mouse kidney that (in part) determine the level of this glycolipid. GlcCer synthase was found to rise in specific activity with age and increased kidney size, whereas GlcCer glucosidase was found to decrease with age; both enzyme changes act to elevate the level of kidney GlcCer and point to the level of this lipid as a determinant of kidney size. The increase in synthase was especially rapid in male kidney, consistent with the more rapid growth of male kidney. Testosterone injection into both males and females produced elevated levels of GlcCer synthase, decreased levels of the hydrolase, and more rapid growth. Injection of 17 beta-estradiol, which produced slow or negative kidney growth, caused the synthase activity to decrease in female mouse kidney and the glucosidase activity to rise in both sexes. Thus the changes in kidney size produced by the two hormones paralleled the changes in GlcCer level predicted by the hormone effects on the two enzymes. In liver, estradiol produced increases in both enzymes but only the male liver increased in size. Testosterone did not affect the liver. The testes grew with age but the activities of both enzymes decreased.
Periventricular lesions block natriuresis to hypertonic but not isotonic NaCl loads
Authors: McKinley M. J. , Lichardus B. , McDougall J. G. , Weisinger R. S.
Published: December 2017

The renal excretion of Na and water after an intravenous load of hypertonic or isotonic saline was studied in conscious sheep in which periventricular tissue in the region of the lamina terminalis had been ablated. Hypertonic saline (3.4-4.2 mmol/l) was infused at 0.06 mmol.kg-1.min-1 for 40 min into the jugular vein. Plasma Na concentration increased 5 mmol/l, and in normal sheep a natriuresis and increase in glomerular filtration rate ensued during the next hour. Such a natriuretic effect did not occur in sheep with periventricular lesions. By contrast, intravenous infusion of isotonic saline (30 ml/kg body wt, i.e., 0.23 mmol.kg-1.min-1 for 20 min) caused similar increase in renal Na excretion in normal sheep and sheep with periventricular lesions. When the same intravenous load of NaCl (0.23 mmol.kg-1.min-1 for 20 min) was administered as hypertonic 20% NaCl, ablation of periventricular tissue greatly impaired the excretion of this Na load. We suggest that the periventricular tissue in the region of the lamina terminalis has a role in regulation of renal Na excretion in conditions where the plasma Na concentration increases. This tissue is also involved in osmoregulatory thirst and vasopressin secretion. We further propose that increased renal Na excretion in response to hypernatremia is another cerebrally mediated osmoregulatory response.
Glucose and amino acid metabolism in chronic renal failure: effect of insulin and amino acids
Authors: Castellino P. , Solini A. , Luzi L. , Barr J. G. , Smith D. J. , Petrides A. , Giordano M. , Carroll C. , DeFronzo R. A.
Published: December 2017

The effects of hyperinsulinemia and hyperaminoacidemia on glucose and amino acid metabolism were examined in 16 control and 13 chronic renal failure (CRF) patients under two conditions: 1) euglycemic hyperinsulinemia and 2) amino acid infusion. All studies were performed with continuous indirect calorimetry and [1–14C]leucine infusion. In CRF patients insulin-mediated whole body glucose metabolism was reduced by 35% (4.41 +/- 0.50 vs. 6.76 +/- 0.73 mg.kg-1.min-1, P less than 0.01), primarily due to a decrease in nonoxidative glucose disposal (1.70 +/- 0.70 vs. 4.32 +/- 0.60 mg.kg-1.min-1, P less than 0.01); glucose oxidation was similar in both groups. In the postabsorptive state total leucine turnover (1.56 +/- 0.06 vs. 1.75 +/- 0.06), leucine oxidation (0.25 +/- 0.01 vs. 0.30 +/- 0.01), and nonoxidative leucine disposal (1.29 +/- 0.06 vs. 1.40 +/- 0.07 mumol.kg-1.min-1) were reduced in CRF vs. control subjects (all P less than 0.05). In response to hyperinsulinemia, endogenous leucine flux (index of proteolysis), leucine oxidation, nonoxidative leucine disposal (NOLD) (index of protein synthesis), and net leucine flux into protein were similar in CRF and control subjects. In contrast, the ability of hyperaminoacidemia to enhance NOLD (1.54 +/- 0.11 vs. 2.10 +/- 0.10 mumol.kg-1.min-1, P less than 0.01) and net leucine balance (0.27 +/- 0.05 vs. 0.41 +/- 0.05, P less than 0.05) was reduced in CRF patients.(ABSTRACT TRUNCATED AT 250 WORDS)
PGE2 inhibits water permeability at a post-cAMP site in rat terminal inner medullary collecting duct
Authors: Nadler S. P. , Zimpelmann J. A. , Hebert R. L.
Published: December 2017

To assess sites and mechanism of action of prostaglandin E2 (PGE2) on water permeability (PF), we determined PGE2 effects on antidiuretic hormone (ADH)- and adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated PF in rat terminal inner medullary collecting ducts perfused in vitro. PGE2 (10(-7) M) reversibly inhibited ADH-stimulated PF (1.131 +/- 192 to 532 +/- 208 microns/s). In contrast to that observed in rabbit, PGE2 also inhibited an established PF response to the exogenous cAMP analogue 8-p-(chlorophenylthio)-cAMP (696 +/- 107 to 399 +/- 99 microns/s). PGE2 alone had no effect on PF. The protein kinase C inhibitor staurosporine (10(-8) M) blocked PGE2-mediated inhibition of cAMP-stimulated PF. PGE2 caused a rapid spikelike increase in intracellular calcium [( Ca2+]i) followed by a stable elevation above basal values. Only the latter effect was abolished in a zero calcium bath. Neither staurosporine nor cAMP altered the [Ca2+]i response. These studies are the first to demonstrate PGE2-mediated inhibition of an established PF response to cAMP independent of changes in intracellular cAMP. The pattern of [Ca2+]i release and sensitivity to staurosporine suggests that this effect is mediated via signaling through phospholipase C. The results underscore the importance of species differences, axial heterogeneity, and/or in vivo conditioning for functional expression of cellular signaling pathways.
Cholinergic stimulation of phosphoinositide metabolism in isolated rat glomeruli
Authors: Meneton P. , Bloch-Faure M. , Guillon G. , Chabardes D. , Morel F. , Rajerison R. M.
Published: December 2017

Cholinergic effects on kidney function have been observed in some mammals but the intrarenal localization and the cellular mechanisms of these effects are poorly defined to date. The aim of this work was to study the effects of carbachol on phosphoinositide metabolism in freshly isolated rat glomeruli labeled with myo-[3H]inositol. Carbachol rapidly and markedly stimulates phosphoinositide metabolism with a 50% effective concentration of 3 microM. The enormous magnitude of the response is enlightened by the use of 10 mM lithium, which provokes in the presence of the agonist a large accumulation of inositol phosphates and a corresponding depletion of cellular free inositol. The response is inhibited by 85% by pirenzepine, is pertussis toxin insensitive, and shows no desensitization at maximum dose of carbachol up to 40 min of stimulation.
Selected polyclonal antibodies and ADH challenge in frog urinary bladder: a label-fracture study
Authors: Calamita G. , Valenti G. , Svelto M. , Bourguet J.
Published: December 2017

It is clearly established that the changes induced by antidiuretic hormone (ADH) in its target epithelial cells result from the insertion in the apical membrane of new components that contain channels for water. We have already undertaken an initial study of these channels by raising polyclonal antibodies against Triton X-100 apical extracts from ADH-treated bladders and approached their purification by different adsorption steps. In the present study, we used the label-fracture technique to investigate the localization of the binding sites of the obtained polyclonal antibodies on the apical membrane of ADH-stimulated frog urinary bladder. The results obtained clearly demonstrated a preferential labeling by the selected antibodies of morphological structures such as the groove arrays and the fusion images that are generally accepted as being involved in ADH-induced changes in water permeability of the apical membrane.
A servo-control system for open- and closed-loop blood pressure regulation
Authors: Nafz B. , Persson P. B. , Ehmke H. , Kirchheim H. R.
Published: December 2017

An electropneumatic servo-control system is described that can reduce and control arterial blood pressure in experimental animals. The device has been proved useful in the analysis of pressure-dependent physiological processes and allows the following two modes of operation: 1) a conventional open-loop setting that will reduce arterial pressure to a preselected set point and 2) a closed-loop mode that enables an adjustment to a dynamic pressure set point (i.e., the controlled pressure is reduced to a constant value below a reference pressure). A pneumatic servo-control mechanism was chosen to provide minimal control latency. The accuracy of the system under physiological conditions is well within +/- 1 mmHg. The device can be useful in a number of studies demanding a precise regulation of local arterial pressure, such as experiments on blood flow autoregulation, arterial baroreceptor reflexes, and all experiments involving the study of pressure-dependent excretory and incretory functions of the kidney. The closed-loop setting is useful for studying physiological feedback systems.
Selective decrement of anionic immunoglobulin clearance after induced renal hemodynamic changes in diabetic patients
Authors: Di Mario U. , Bacci S. , Morano S. , Pugliese G. , Pietravalle P. , Andreani D. , Morabito S. , Simonetti B. , Pierucci A.
Published: December 2017

The charge permselectivity of proteins was evaluated in diabetic patients after systemic and renal hemodynamic changes induced by an intravenous injection of an angiotensin-converting enzyme inhibitor (captopril) or of clonidine. Anionic immunoglobulin clearance (IgG4) was compared with that of total immunoglobulins, which have the same size but are mostly cationic, and of albumin. Ten type I hypertensive diabetic patients (group 1), 10 type 2 hypertensive diabetic patients (group 2), 5 type 1 normotensive diabetic patients (group 3), 10 subjects with essential hypertension (group 4), and 7 normal volunteers (group 5) received an intravenous injection of captopril (25 mg/100 ml in 5 min). Twelve of the hypertensive diabetic patients underwent a second provocative test with clonidine (150 micrograms/100 ml) (group 6) or placebo (100 ml saline) (group 7) with the same procedure. None of the patients had clinical nephropathy or other disorders. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured before and during the tests. A significant decrease in diastolic blood pressure was observed in groups 1, 2, 4, and 6, together with an increase in the GFR and RPF values in groups 1, 2, 3, and 4 only, as well as a decrease in renal vascular resistances in groups 1, 2, 3, 4, and 6. Both clearances and fractional clearances of IgG4 and IgG decreased after captopril in groups 1 and 2.2+ The decrease in IgG4 clearance was correlated to that of renal vascular resistances in group 1 patients. A significant decrease in the anionic-cationic immunoglobulin ratio (IgG4/IgG) was observed in groups 1, 2, and 3.(ABSTRACT TRUNCATED AT 250 WORDS)
Basolateral 3-O-methylglucose transport by cultured kidney (LLC-PK1) epithelial cells
Authors: Mullin J. M. , Kofeldt L. M. , Russo L. M. , Hagee M. M. , Dantzig A. H.
Published: December 2017

In previous work we demonstrated the similarity of basolateral sugar transport of LLC-PK1 renal epithelia to basolateral kidney sugar transport using 2-deoxy-D-glucose as a substrate. In this study we first examine a central limitation to use of 2-deoxyglucose for basolateral sugar transport study in LLC-PK1 epithelia, namely, a shift of the rate-limiting step in uptake from transport to phosphorylation. Use of 3-O-methylglucose avoids this complication because it is not phosphorylated. However, use of 3-O-methylglucose requires much shorter incubation periods to examine linear rates of uptake (steady state is reached by 60 s at 22 degrees C for 0.1 mM 3-O-methylglucose). As was true for 2-deoxyglucose, apical uptake of 3-O-methylglucose was only a fraction of total uptake. Basolateral uptake was characteristically more sensitive to phloretin and cytochalasin B inhibition, relative to phlorizin. Inhibition studies indicate a requirement for a free hydroxyl on C-1 carbon of the pyranose ring, as is characteristic for renal basolateral sugar transport. Kinetic analysis indicates a single transport system with a Km of 10.9 mM and Vmax of 17.2 pmol.micrograms DNA-1.15 s-1. Subconfluent, undifferentiated LLC-PK1 cells show a similar Km (12.7 mM) but a ninefold higher Vmax (166.2 pmol.micrograms DNA-1.15 s-1). Stimulation of 3-O-methylglucose transport rate in confluent cultures by phorbol ester is relatively small (less than 100%) compared with effects on other somatic cells. The uptake rate of 3-O-methylglucose is not affected by glucose starvation, but subsequent refeeding with glucose-containing medium does significantly stimulate uptake.
Injury-induced changes in cytosolic Ca2+ in individual rabbit proximal tubule cells
Authors: Smith M. W. , Phelps P. C. , Trump B. F.
Published: December 2017

Cell injury was studied in cultured rabbit proximal tubular epithelial cells using digital-imaging fluorescent microscopy to relate changes in cytosolic Ca2+ ([Ca2+]i) to bleb formation and cell death. Fura-2-loaded cells were treated in normal (1.37 mM) and low (less than 5 microM) extracellular Ca2+ ([Ca2+]e) with 1) inhibitors of glycolysis (iodoacetate) and/or mitochondrial oxidation (KCN), 2) thiol-modifying reagents (N-ethylmaleimide, p-chloromercuribenzene, and p-chloromercuribenzene sulfonate), and 3) Ca2+ ionophore (ionomycin). All three types of injury produced both [Ca2+]e-independent and [Ca2+]e-dependent increases in [Ca2+]i. KCN + iodoacetate +/- [Ca2+]e did not produce blebbing or death within 60-90 min. Thiol modifiers and ionomycin produced blebbing, which correlated with sustained threefold or greater elevations of [Ca2+]i and loss of viability only after [Ca2+]i had risen severalfold. Blebbing and cell death could be prevented or delayed by treatment in low [Ca2+]e. Trypsin (x0.5) caused a transient (less than 5 min) elevation in [Ca2+]i as well as increases in intracellular Ca2+ pools.
Intracellular pH in OK cells. II. Effects of temperature on cell pH
Authors: Graber M. , Barry C. , Dipaola J. , Hasagawa A.
Published: December 2017

Intracellular pH (pHi) is known to acidify as temperature rises. It has been proposed that this relationship reflects the temperature dependence of the dissociation constant of intracellular buffers. The purpose of this study was to evaluate whether H+ production and membrane acid/base transport events also contribute to the temperature dependence of pHi. This relationship was studied by means of the 490/450-nm fluorescence of 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, to measure pHi of OK cells grown on cover slips and perfused in a thermostated chamber. As temperature was increased from 12 degrees C, pHi progressively acidified, until a precipitous and large alkalinization appeared at 40-45 degrees C. We specifically examined the range from 25 to 37 degrees C, over which pHi acidified by 0.32 units from 7.50 to 7.18. The three major components that regulate pHi in the OK cell were quantitated as follows: H+ production, H+ extrusion via Na(+)-H+ antiport, and the passive H+ leak from buffer to cell. Relative to the rate at 25 degrees C, acid production at 37 degrees C increased by 129% (3.82 +/- 0.78 vs. 8.76 +/- 1.12 mmol.l-1.min-1). The recovery of pHi after NH4Cl loading was used to measure the rate of Na(+)-H+ antiport, and in Na(+)-free depolarized cells the magnitude of passive H+ conductance through the leak pathway. Compared with the rate at 25 degrees C, at 37 degrees C the Na(+)-H+ antiport increased by 26% (1.25 +/- 0.22 vs. 1.58 +/- 0.25 mmol.l-1.min-1) and the H+ permeability increased by 140% (0.005 +/- 0.001 vs. 0.012 +/- 0.003 cm/s).(ABSTRACT TRUNCATED AT 250 WORDS)
Renal adaptation to low-phosphate diet in diabetic rats
Authors: Abraham M. I. , Woods R. E. , Breedlove D. K. , Kempson S. A.
Published: December 2017

Insulin stimulates the Na(+)-Pi cotransport system in the brush-border membrane (BBM) of the renal proximal tubule, and an acute decrease in plasma insulin leads to a decrease in renal reabsorption of Pi. It has been proposed that insulin may play a role in the rapid renal adaptation to dietary deprivation of Pi. This hypothesis was tested using rats with low plasma insulin due to streptozotocin-induced diabetes. Both control and diabetic rats were housed in metabolic cages and fed either a normal Pi diet or a low Pi diet for 3 days. At the end of the third day, BBM vesicles were prepared from renal cortex and Na(+)-Pi cotransport was measured. At the whole kidney level, diabetic rats showed a normal adaptive response. There was a prompt and marked decrease in urinary Pi excretion when the rats ate a low Pi diet. At the BBM level, however, the adaptive response was absent. There was no increase in Na(+)-Pi cotransport in diabetic rats fed low Pi diet. Treatment of diabetic rats with exogenous insulin before feeding low Pi diet restored the adaptive increase in Pi transport by BBM. Insulin appears to be required for the adaptation of proximal tubule Pi transport to low Pi diet. In the absence of this adaptation in proximal tubule BBM, a compensatory response in the kidney may produce an increase in Pi reabsorption in later segments of the nephron.
Renal nerve effects on renal adaptation to changes in sodium intake during ovine pregnancy
Authors: Aberdeen G. W. , Cha S. C. , Mukaddam-Daher S. , Nuwayhid B. S. , Quillen E. W.
Published: December 2017

To assess the possibility of an enhanced role of renal nerves in the control of urinary sodium excretion (UNaV) and fluid homeostasis during pregnancy, urine output, UNaV, and urinary potassium excretion were assessed hourly for 3 days before and for 6 days after a step reduction in total daily sodium intake from 400 to 40 mmol. Studies were performed in normal conscious sheep (4 nonpregnant and 4 pregnant). Each animal was prepared with a divided bladder so that urine could be collected simultaneously from one normally innervated and one denervated kidney. In nonpregnant ewes, ratios of the rates of excretion by denervated vs. innervated kidneys for UNaV averaged 1.00 +/- 0.07 under steady-state conditions at high levels of sodium intake. This ratio was not different at the low-sodium-intake state. In contrast, this ratio was 1.15 +/- 0.07 at high sodium intake and 1.13 +/- 0.03 at low sodium intake in pregnant ewes. The ratios at both steady-state intake levels were different (P less than 0.05) between nonpregnant and pregnant sheep. During the transition between sodium intake states, these ratios were unchanged in nonpregnant animals, whereas pregnant animals exhibited peak ratios of 2.20 +/- 0.39 (P less than 0.05), indicating sodium wasting by the denervated kidneys. In summary, the data suggest that renal nerve activity may not be completely suppressed by high sodium intakes in pregnant sheep. Furthermore, the renal nerves have an enhanced influence on sodium conservation during and after the transition from high- to low-sodium-intake states during pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)
Growth hormone regulates ammoniagenesis in canine renal proximal tubule segments
Authors: Chobanian M. C. , Julin C. M. , Molteni K. H. , Brazy P. C.
Published: December 2017

To determine whether growth hormone (GH) directly affects ammoniagenesis in the renal proximal tubule, ammonia production was measured in suspensions of isolated canine renal proximal tubule segments (IPTs) incubated with 2.5 mM L-glutamine and varying concentrations of human growth hormone (hGH). Ammonia production from IPTs significantly increased by nearly threefold in the presence of hGH (10(-6) M) at 60 min. This increase was dose dependent, with as little as 10(-9) M hGH significantly stimulating ammonia production. In addition, hGH enhanced glucose production when lactate, alanine, and succinate replaced L-glutamine as substrate. hGH significantly stimulated ammonia production when IPTs were incubated at alkalotic and neutral pH. The effect of hGH was lost at acidic pH. When hGH was added to IPTs incubated under Na(+)-equilibrated conditions, ammonia production was not different from control. hGH stimulated ouabain-sensitive Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity by 8.1 +/- 1.1% in basolateral membranes isolated from IPTs. hGH stimulation of proximal tubule ammonia production from L-glutamine occurs at physiological concentrations of hGH and when the extracellular-to-intracellular Na+ gradient favors L-glutamine transport. This effect is associated with an increase in basolateral Na(+)-K(+)-ATPase activity. The data suggest a role for hGH in the regulation of renal acid-base metabolism under physiological conditions in which increased net acid excretion is important.
Cyclic nucleotides alter intracellular free Mg2+ in renal epithelial cells
Authors: Dai L. J. , Quamme G. A.
Published: December 2017

Intracellular Mg2+ plays an important role in cell physiology. Studies were performed on MDCK cells and primary cortical thick ascending limb (CTAL) cells to determine hormonal influences on intracellular Mg2+ control. Free Mg2+ ([Mg2+]i) was measured by fluorescence with mag-fura-2. Addition of 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcG-MP, 10(-4) M) to subconfluent MDCK cells resulted in rapid increases in [Mg2+]i from basal levels of 552 +/- 6 microM to peak concentrations of 682 +/- 5 microM, whereas 8-BrcAMP (10(-4) M) led to significant decreases in [Mg2+]i from 538 +/- 5 to 362 +/- 17 microM. These effects of cyclic nucleotides were dose dependent with half-maximal concentrations (EC50) of approximately 10(-5) M for both increments in [Mg2+]i with cGMP and decrements in [Mg2+]i with cAMP. Atrial natriuretic peptide (ANP) and cGMP increased Mg2+ in porcine primary CTAL cells from 525 +/- 12 to 592 +/- 18 microM and from 538 +/- 8 to 609 +/- 18 microM, respectively. The increment in [Mg2+]i with ANP was dose responsive with EC50 values of approximately 10(-11) M suggesting that these effects may be of physiological importance. Parathyroid hormone and calcitonin and their second messenger, cAMP, diminished Mg2+ by approximately 80 microM. The EC50 value for calcitonin was in the order of 10(-9) M. The changes in [Mg2+]i, whether increases with ANP or cGMP and decreases with PTH, calcitonin, or cAMP, were rapid in nature and independent of changes in intracellular free Ca2+ concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
Intrarenal DA2 dopamine receptor stimulation in the conscious dog
Authors: Siragy H. M. , Felder R. A. , Peach M. J. , Carey R. M.
Published: December 2017

DA2 dopamine receptors are present in renal blood vessels and glomeruli. Stimulation of DA1 dopamine receptors leads to renal vasodilation, diuresis, and natriuresis, but a functional role for renal DA2 receptors is largely unknown. We investigated the possible role of DA2 receptors in the control of renal function by intrarenal infusion of a highly specific DA2 agonist, LY 171555 (LY), in conscious uninephrectomized dogs (n = 5) in metabolic balance at sodium intake of 40 meq/day. The infusion of LY at 0.5 pmol.kg-1.min-1 did not change the urinary sodium excretion or renal hemodynamic function. A significant dose-dependent antidiuresis (F = 8.1, P less than 0.0001) and antinatriuresis (F = 93.3, P less than 0.0001) and a decrease in filtration fraction (F = 2.3, P less than 0.02) occurred as the LY dose was increased from 1.0 to 10.0 pmol.kg-1.min-1. There were no changes in systemic plasma renin activity, plasma aldosterone concentration, or mean arterial pressure during intrarenal LY administration. These data suggest that intrarenal DA2 receptor stimulation with LY decreases renal sodium excretion in part by hemodynamic mechanisms. Renal dopamine may act at vascular and/or glomerular DA2 receptors to modulate renal function.
Cytoplasmic dilution induces antidiuretic hormone water channel retrieval in toad urinary bladder
Authors: Harris H. W. , Botelho B. , Zeidel M. L. , Strange K.
Published: December 2017

Antidiuretic hormone (ADH) increases the osmotic water permeability (Pf) of the toad urinary bladder by insertion of water channels into the apical cell membrane. Transepithelial water flow (Jv) reduces Pf by inducing endocytosis of apical water channels despite continuous ADH stimulation. This phenomenon is termed flux inhibition. We wished to determine whether cytoplasmic dilution or transcellular Jv causes flux inhibition because both have been proposed previously as a primary regulatory mechanism for this process. Apical membrane endocytosis was quantified by monitoring the uptake of the fluid phase marker fluorescein isothiocyanate dextran (FITC-dextran). FITC-dextran fluorescence was monitored in Triton X-100 extracts of epithelial cells as the ratio of total tissue fluorescence compared with background fluorescence. The background was defined as cellular autofluorescence and nonspecific tissue staining due to the presence of small amounts of free fluorescein contaminating the FITC-dextran. FITC-dextran uptake measured under symmetric isotonic (220 mosmol/kgH2O) conditions in either the absence (1.0 +/- 0.4 SD; n = 14) or presence (1.3 +/- 0.3; n = 4) of ADH was not statistically different from that of background. In contrast, flux inhibition induced by a 180 mosmol/kgH2O apical-to-basolateral osmotic gradient increased FITC-dextran uptake to 3.4 +/- 1.3 (n = 7). FITC-dextran uptake was identical in bladders exposed to symmetric hypotonic (150 mosmol/kgH2O) solutions during ADH (3.6 +/- 0.9; n = 6) or adenosine 3',5'-cyclic monophosphate (3.1 +/- 0.4 fold; n = 3) stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)