bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Ringer fluid on regional blood flow and filtration rate in the cat kidney
Authors: Rasmussen S. N. , Andersen J. S. , Nissen O. I.
Published: December 2017

The larger subcapsular veins of the in situ cat kidney were cut open near the hilus and occluded between the slits and the common renal vein, thus permitting separation and direct measurement of venous outflows from the superficial (outer cortex) and deep (inner cortex plus medulla) drainage area. The direct recording of venous outflow in the two areas combined with plasma inulin and protein analyses provided consecutive determinations of the rate of glomerular filtration and arterial inflow of both areas. Our primary result is the demonstration of a regional difference in the renal response to extracellular isotonic volume expansion. Infusion of Ringer fluid at a moderate rate (1.0-2.0 ml X min-1) increased both blood flow (RBF) and glomerular filtration rate (GFR) in both areas; however, the RBF response was proportionately greater in the deep area and the GFR response was proportionately greater in the superficial area. Compared with a noninfused control series, statistically significant differences occurred after about 1 h of infusion. After 80 min, average RBF had increased by 33 and 20%, while average GFR had increased by 31 and 54% in the deep and in the superficial areas, respectively. To reveal direct renal effects of the Ringer fluid, the site of infusion was shifted alternately between the renal artery and the jugular vein. The results suggest that the changes in blood flow are elicited indirectly by neural or humoral mechanisms.
Renal apical membrane cholesterol and fluidity in regulation of phosphate transport
Authors: Molitoris B. A. , Alfrey A. C. , Harris R. A. , Simon F. R.
Published: December 2017

Renal proximal tubule cells adapt to dietary phosphate (Pi) restriction by increasing Pi transport independent of parathyroid hormone, vitamin D metabolites, or serum Ca2+. To determine the underlying cellular mechanism(s), brush border (BBM) and basolateral membranes (BLM) were isolated from growing male rats fed a synthetic diet containing variable levels of Pi (0.1-1.4%). Dietary Pi restriction was without effect on either BBM or BLM total lipid phosphorus, individual phospholipid species, or BLM Na+-K+-ATPase specific activity. However, dietary Pi restriction (0.1 vs. 1.0%) did cause a significant reduction in BBM but not BLM cholesterol (0.45 vs. 0.41 mumol/mg protein). Brush border membrane cholesterol was inversely correlated with the tubular reabsorption of Pi (r = 0.77, P less than 0.01) over a broad range (99.9-46.2%). Arrhenius analysis of two intrinsic BBM enzymes revealed a significant reduction in the breakpoint temperature for alkaline phosphatase but no change for Mg2+-ATPase. Fluorescence polarization studies showed increased BBM inner core fluidity due to an alteration in neutral lipids but not phospholipid, fatty acid, or protein membrane components. These data demonstrate that the BBM can regulate its cholesterol content independent of the BLM. Furthermore, they suggest that adaptation to dietary Pi restriction involves a reduction in BBM cholesterol, which may be mediated by an increase in membrane fluidity.
pH gradient-dependent increased Na+-H+ antiport capacity of the rabbit remnant kidney
Authors: Nord E. P. , Hafezi A. , Kaunitz J. D. , Trizna W. , Fine L. G.
Published: December 2017

The adaptative response of the renal proximal tubule to a reduction of renal mass was studied in brush border membrane vesicles prepared from the solitary remnant kidney (RK) of subtotally nephrectomized rabbits. The in vivo acid-base status of RK and sham-operated controls (SK) was similar. In the absence of organic solutes, Na+ flux across the membrane demonstrated features of Na+-H+ antiport, i.e., stimulation by a transmembrane pH gradient and inhibition by amiloride. Kinetic parameters for Na+-H+ antiport were derived with different experimental protocols. In the presence of an opposing H+ gradient and over a limited range of Na+ concentration, JNamax was enhanced 65% in RK vesicles compared with SK vesicles and KtNa was unchanged. The enhanced JNamax was not apparent under H+ equilibrium conditions, Comparable values for JNamax and KtNa were obtained by studying RK vesicles at external Na+ concentrations of 0-200 mM and resolving uptake into a substrate component, representing Na+-H+ antiport, and a nonsaturable diffusive component. The apparent Na+ permeability (P'Na) of RK vesicles was identical to the P'Na of normal kidney vesicles, under both H+ gradient and H+ equilibrium conditions. H+ permeability, measured with acridine orange, was also the same in RK and SK vesicles. These studies demonstrate that in the remnant kidney model of chronic renal insufficiency there is an increase in the JNamax of the Na+-H+ antiporter in the luminal membrane of the proximal tubule that is revealed only under transmembrane H+ gradient conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Tubular reabsorption delay of amino acids in the rabbit kidney
Authors: Foulkes E. C.
Published: December 2017

Estimates were obtained both with a rapid-transient technique and under steady-state conditions of the average time required for filtered solutes in the intact rabbit kidney to cross tubular epithelium from tubular lumen into the peritubular inulin space. This interval, defined as the transepithelial passage time, was relatively short (about 15 s) for glucose, in agreement with earlier results in the dog. In contrast, several amino acids required an average transepithelial passage time of about 40 s. Values for aspartate could only be obtained when its large basolateral uptake was inhibited by excess succinate. The long transepithelial passage time may be due to the slow extrusion of reabsorbed amino acids across basolateral cell membranes. This hypothesis was supported by the extent of tissue accumulation of amino acids during reabsorption. Even though basolateral transfer may thus limit the linear rate of movement of filtered amino acids across the epithelium, the step determining fractional absorption from the lumen is situated at the brush border.
Binding of aldosterone metabolites in isolated tubular segments
Authors: Farman N. , Pradelles P. , Bonvalet J. P.
Published: December 2017

High-performance liquid chromatography (HPLC) analysis was performed on tissue extracts from whole kidney cortex (after in vivo injection or in vitro incubation with [3H]-aldosterone ([3H]A], from products bound to aldosterone receptors in cytoplasmic and nuclear fractions, and from the convoluted (PCT) and straight (PR) portion of the proximal tubule and cortical collecting tubule (CCT) isolated by micro-dissection after in vitro incubation with [3H]A (10 and 80 nM). After in vitro incubation of whole tissue, about 10% of the radioactivity corresponded to three groups of metabolites, two polar ones, which eluted earlier than aldosterone, and one less polar, which eluted later than aldosterone. When HPLC analysis was performed on bound products, after removal of free [3H]A, only one group of polar metabolites was detected (about 8% of the radioactivity) in addition to native [3H]A in the cytoplasmic and nuclear fractions. The binding of polar metabolites was nonspecific (nondisplaceable) and did not vary with incubation time and aldosterone concentration. In isolated tubules, in addition to [3H]A, an early peak of polar metabolites, corresponding to that observed in bound fractions, was present in PCT (10%) and in PR and CCT (20-25%). Other metabolites were not found in isolated tubules. We conclude the following: 1) The kidney is able to form at least three groups of aldosterone metabolites in small amounts. 2) Only one of them (more polar) was detected, as a nonspecifically bound product, in cellular fractions containing hormone-receptor complexes after removal of free [3H]A. Other metabolites were removed with free [3H]A. 3) These polar metabolites were found in both mineralocorticoid target segments such as CCT and in classically nontarget segments such as the proximal tubule. 4) The nonspecificity of the binding of polar metabolites and the absence of selective localization along the nephron suggest that they have no major mineralocorticoid action.
Importance of the kidney in the correction of chloride-depletion alkalosis in the rat
Authors: Craig D. M. , Galla J. H. , Bonduris D. N. , Luke R. G.
Published: December 2017

Correction of chloride-depletion alkalosis (CDA) may involve renal as well as extrarenal mechanisms. To determine the relative contribution of these mechanisms in a rat model of CDA produced by peritoneal dialysis (PD), we studied six groups of anesthetized Sprague-Dawley rats after PD. Groups II-IV and IIa were subjected to functional bilateral nephrectomy, and groups I and Ia were sham-operated. Groups I, Ia, II, and IIa were infused with isotonic fluid containing 70 mM Cl- and 40 mM HCO3-; the infusate in group III was 140 mM Cl- and in group IV, 70 mM neutral PO4 was substituted for Cl-. Groups I and Ia were infused at 0.5 ml . h-1 X 100 g body wt-1 and groups II, IIa, III, and IV at 0.25 ml . h-1 X 100 g-1. After 3 h of infusion, early partial correction with reciprocal changes in plasma Cl (+6.1 +/- 1.9 mmHg) and total CO2 (-6.0 +/- 0.8 meq/liter) occurred (P less than 0.01) only in group I. Hypokalemia (3.1 +/- 0.1 meq/liter) also occurred only in group I. The responses of groups Ia and IIa studied at 5 h were similar to those of groups I and II. These data suggest that the kidney, and not extrarenal mechanisms, is primarily responsible for the correction of CDA during infusion of chloride.
Angiotensin II and eicosanoids in the control of glomerular size in the rat and human
Authors: Scharschmidt L. A. , Douglas J. G. , Dunn M. J.
Published: December 2017

We examined the possibility that glomerular prostaglandin E2 (PGE2) regulates the action of angiotensin II (ANG II) on mesangial contraction and filtration surface area. Using isolated rat glomeruli we indirectly assessed mesangial contraction and filtration surface area through measurements of glomerular planar surface area (GPSA) by image-analysis microscopy. ANG II reduced GPSA by approximately 20% in human and rat glomeruli, with threshold concentrations of 1 X 10(-13) M and maximum effect at 5 X 10(-11) M ANG II. Inhibition of glomerular PG synthesis with indomethacin or meclofenamate potentiated the threshold response of ANG II to reduce GPSA. Arachidonic acid (5 micrograms/ml) blunted both the threshold and the maximum responses of GPSA to ANG II. PGE2, 10(-8) and 10(-9) M, also decreased glomerular contraction to ANG II. Endoperoxide (EP) analogues decreased GPSA and EP 045, a thromboxane A2 (TXA2) receptor blocker, eliminated the contractile responses of glomeruli to the EP analogues. Authentic TXA2, synthesized from sheep platelet microsomes, also reduced GPSA. We conclude that glomerular products of arachidonate cyclooxygenation may either relax or contract the mesangium, thereby preserving or reducing filtration surface area. PGE2 exerts protective actions to reduce the mesangial contraction of ANG II, primarily through postreceptor effects. TXA2 may decrease glomerular filtration rate in certain diseases through direct actions on the mesangium.
Effect of amiloride on urinary and renal kallikrein in the rat
Authors: Croxatto H. R. , Corthorn J. , Roblero J. , Villalon P. , Perez F.
Published: December 2017

A single intraperitoneal injection of amiloride in the range of 2.7, 5.4, 10.9, and 21 mumol/100 g body wt in female adult rats produced, in the two successive periods of 4 h following its administration, a significant decrease in the urinary excretory rate of kallikrein. Amiloride, 10.9 mumol/100 g body wt, which significantly reduced active kallikrein, also decreased, but less significantly, the trypsin-activated kallikrein in the urine. The fall in the excretory rate of kallikrein cannot be explained by its enzymatic inhibition by amiloride, since the inhibition was only present at higher concentrations. In hyperhydrated rats amiloride did not change the kallikrein excretory rate in the urine collected within 4 h after the injection. Rats simultaneously injected with 7.6 mumol/100 g body wt furosemide and 10.9 mumol/100 g body wt amiloride excreted levels of kallikrein similar to those found in rats injected with furosemide alone. The kidneys of rats removed after 4 h of administration of 10.9 mumol/100 g body wt amiloride showed a significant lowering of the kallikrein activity compared with the respective controls. The decrease of renal kallikrein tended to be similarly pronounced in those rats that received amiloride and furosemide simultaneously. These results confirm the depressive effect of amiloride on kallikrein excretion, which may be explained by an inhibitory action on kallikrein release, activation, and synthesis by the renal cells.
Effects of increase in plasma calcium concentration on renal handling of NaCl and NaHCO3
Authors: Mercier O. , Prigent A. , Bichara M. , Paillard M. , Leviel F.
Published: December 2017

Recollection micropuncture experiments were carried out in thyroparathyroidectomized volume-expanded rats to examine the effects of CaCl2 infusion on the renal and nephronal segmental handling of chloride and bicarbonate. In group 1A, a 0.23 mM increase in plasma calcium concentration [delta(Ca)P] reduced urinary total CO2 (tCO2) excretion from 401 +/- 90 to 166 +/- 43 nmol X min-1 X g kidney wt-1 (P less than 0.05), whereas tCO2 filtered load was slightly diminished from 34,086 +/- 3,627 to 28,904 +/- 2,496 nmol X min-1 X g kidney wt-1 (NS). In group 1B [delta(Ca)P, 0.73 mM], whole kidney filtered loads were significantly lowered, as was urinary tCO2 excretion; however, urinary excretion of sodium, chloride, and water remained constant. Calcium infusion inhibited the proximal reabsorption of chloride 25% and water 16%; however, calcium infusion caused the end-proximal tCO2 concentration to significantly decrease so that the absolute and fractional tCO2 reabsorption remained constant. In group 2 [delta(Ca)P, 0.43 mM], whole kidney filtered load was unchanged for chloride and water but decreased for bicarbonate; urinary tCO2 excretion was reduced, whereas chloride and water excretion increased. In this group, early distal micropunctures evidenced that superficial single-nephron filtered loads were significantly reduced during calcium infusion; early distal chloride delivery was enhanced from 348 +/- 32 to 441 +/- 36 pmol X min-1 X g kidney wt-1 (P less than 0.05), whereas tCO2 delivery decreased from 47 +/- 5 to 38 +/- 4 pmol X min-1 X g kidney wt-1 (P less than 0.05). In group 3 of time control animals, whole kidney and early distal data were unchanged during second period. In group 4, H+ secretion in the collecting duct, as assessed by analyzing the relationship between urine-minus-blood PCO2 and urinary bicarbonate concentration in maximally alkaline urine, was not modified during CaCl2 infusion [delta(Ca)P, 0.79 mM]. We conclude that increase in plasma calcium concentration inhibits proximal NaCl and water reabsorption, whereas it stimulates the bicarbonate transport relative to that of chloride, leading to an enhanced proximal and renal bicarbonate-to-chloride reabsorptive ratio that could generate metabolic alkalosis; and decreases urinary bicarbonate excretion by also lowering the bicarbonate filtered load.
Tubuloglomerular feedback responses in the rat during calmodulin inhibition
Authors: Bell P. D.
Published: December 2017

Previously, we have suggested that a cytosolic calcium system participates in the transmission of signals between distal tubular fluid and the glomerular vascular elements. Since the Ca-binding protein calmodulin has been implicated in the intracellular actions of cytosolic Ca, we evaluated the effects of the calmodulin antagonists trifluoperazine (TFP) and calmidazolium (R24571) on tubuloglomerular feedback responses. In the rat, stop-flow pressure (SFP) was measured during retrograde perfusion into the distal tubule at 15 nl/min for 5 min. Perfusion with an isotonic Ringer solution resulted in a decrease in SFP of 12 +/- 1.1 mmHg (n = 34). With the addition of 50-75 microM TFP, SFP was decreased by 11 +/- 1.0 mmHg (n = 24); with 500 microM TFP, SFP feedback responses were 10 +/- 1.2 mmHg (n = 7). During perfusion with 20 microM R24571, SFP decreased by an average of 12 +/- 1.1 mmHg (n = 18). Single-nephron glomerular filtration rate feedback responses during retrograde microperfusion were also unaltered by R24571 (delta 15 +/- 2.5 vs. delta 14 +/- 2.6 nl/min). In the SFP experiments it was observed that the recovery of SFP toward preinfusion values after cessation of perfusion was significantly prolonged in tubules perfused with the calmodulin antagonists. SFP recovery times averaged 65 +/- 5.5 s (control), 104 +/- 9.9 s (50-75 microM TFP), 154 +/- 9.6 s (500 microM TFP), and 116 +/- 9.9 s (20 microM R24571). Accordingly, these results suggest that activation of calmodulin is not required for the transmission of tubuloglomerular feedback signals.(ABSTRACT TRUNCATED AT 250 WORDS)
Phorbol ester-stimulated phosphorylation of basolateral membranes from canine kidney
Authors: Hammerman M. R. , Rogers S. , Morrissey J. J. , Gavin J. R.
Published: December 2017

To determine whether protein kinase C is present in the basolateral membrane of the renal proximal tubular cell, we performed experiments to ascertain whether specific binding of [3H]phorbol 12,13-dibutyrate could be demonstrated in basolateral membranes isolated from canine kidney. Specific binding was demonstrable that was half maximal at between 10(-7) and 10(-8) M phorbol 12,13-dibutyrate. Binding was inhibited by 12-O-tetradecanoylphorbol-13-acetate (TPA) and other tumor-promoting phorbol esters, but not by inactive phorbol esters, including 4 alpha-phorbol. Incubation of basolateral membranes with TPA and phorbol 12,13-dibutyrate, but not with 4 alpha-phorbol, in the presence of submicromolar concentrations of free calcium, enhanced phosphorylation of several proteins demonstrable in autoradiograms of sodium dodecyl sulfate-polyacrylamide gels originating from membranes subsequently exposed to [gamma-32P]ATP for 30 s. Dephosphorylation of [32P]phosphoproteins was observed in gels from membranes incubated with [gamma-32P]ATP over time. TPA-stimulated phosphorylation of one protein band with Mr 135,000 was quantitated and was found to increase as a function of [TPA]. Half-maximal TPA-stimulated phosphorylation of this protein band occurred at slightly less than 10(-9) M TPA. Our findings are consistent with a role for protein kinase C-effected phosphorylation of basolateral membrane proteins in the mediation or modulation of hormonal actions in the proximal tubular cell.
Role of topology in bioenergetics of sodium transport in complex epithelia
Authors: Huf E. G. , Mikulecky D. C.
Published: December 2017

There has been some controversy as to whether in sodium-transporting epithelia (e.g., frog skin, toad urinary bladder) the Na-O2 ratio is independent of the net rate of transepithelial sodium transport or remains constant over a wide range of transport rates. This computer simulation study shows that both views are defensible, depending on whether one wishes to exclude or include “static head” energy in the calculations. This energy arises from intramembrane sodium recirculation, as shown here when applying a multicompartment epithelial membrane model. Assuming reasonable kinetic parameters of a transport model whose sodium transport rate is varied over a wide range by a step-by-step simulated amiloride action, the computations have shown the following. When static head energy (O2 consumption) is excluded from the calculations, the Na-O2 ratio is constant over a wide range of transepithelial sodium flux, up to the tested value of 20 neq X cm-2 X min-1, a “normal” value found in frog skin. The Na-O2 ratios were 19.4 and 28.7 in low- and high-sodium models, respectively. If the static head energy is included in the calculations, the Na-O2 ratios increase with increasing transport rate from zero values to values up to 15.7. These data are in good agreement with laboratory results, as are derived data on phenomenological coefficients and thermodynamic coupling coefficients (LNa = 80, 128; LNa,r = 4.4; Lr = 0.27, 0.58; q = 0.50, 0.90, depending on the chosen model parameters).
Urate transport in the proximal tubule: in vivo and vesicle studies
Authors: Kahn Andrew M. , Weinman Edward J.
Published: December 2017

Pages F789–F798: Andrew M. Kahn and Edward J. Weinman. “Urate transport in the proximal tubule: in vivo and vesicle studies.” Page F793 (right column, bottom of page): “Fig. 3” and “Fig. 4” are reversed.
Platelet-activating factor and the kidney
Authors: Schlondorff D. , Neuwirth R.
Published: December 2017

Platelet-activating factor (PAF) represents a group of phospholipids with the basic structure of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine. A number of different cells are capable of producing PAF in response to various stimuli. The initial step of PAF formation is activation of phospholipase A2 in a calcium-dependent manner, yielding lyso-PAF. During this step arachidonic acid is also released and can be converted to its respective cyclooxygenase and lipoxygenase products. The lyso-PAF generated is then acetylated in position 2 of the glycerol backbone by a coenzyme A (CoA)-dependent acetyltransferase. An additional pathway may exist whereby PAF is generated de novo from 1-alkyl-2-acetyl-sn-glycerol by phosphocholine transferase. PAF inactivation in cells and blood is by specific acetylhydrolases. PAF exhibits a variety of biological activities including platelet and leukocyte aggregation and activation, increased vascular permeability, respiratory distress, decreased cardiac output, and hypotension. In the kidney PAF can produce decreases in blood flow, glomerular filtration, and fluid and electrolyte excretion. Intrarenal artery injection of PAF may also result in glomerular accumulation of platelets and leukocytes and mild proteinuria. PAF increases prostaglandin formation in the isolated kidney and in cultured glomerular mesangial cells. PAF also causes contraction of mesangial cells. Upon stimulation with calcium ionophore the isolated kidney, isolated glomeruli and medullary cells, and cultured mesangial cells are capable of producing PAF. The potential role for PAF in renal physiology and pathophysiology requires further investigation that may be complicated by 1) the multiple interactions of PAF, prostaglandins, and leukotrienes and 2) the autocoid nature of PAF, which may restrict its action to its site of generation.
Use of trypan blue for identifying early proximal convoluted tubules
Authors: Linshaw M. A. , Bauman C. A. , Welling L. W.
Published: December 2017

Proximal convoluted renal tubules (PCT) are difficult to dissect for in vitro study, particularly in newborn animals, and are identified with certainty only when obtained in continuity with their parent glomeruli. We show here that the supravital colloidal dye trypan blue preferentially stains early PCT segments of rabbit in vivo and greatly facilitates their isolation. We also show that trypan blue administration does not adversely affect animal growth rate, kidney weight, or several general measures of kidney function. Using isolated PCT from newborn to adult rabbits, control (unstained) and trypan blue-stained tubules also are found not to differ in lateral membrane surface density, in their ability to maintain normal cell volume or to respond to hypotonic osmotic challenge, and in their swelling rate in isotonic medium after ouabain treatment. We conclude that trypan blue has no adverse effects on PCT cell function while greatly facilitating their isolation for physiological studies.
Role of arginine vasopressin in medullary thick ascending limb on maximal urinary concentration
Authors: Kim J. K. , Summer S. N. , Erickson A. E. , Schrier R. W.
Published: December 2017

Two groups of Sprague-Dawley rats, Harlan (H) and Charles River (CR), were discovered in that the medullary thick ascending limb (MAL) had a profoundly different adenylate cyclase response to arginine vasopressin (AVP). Using these two groups of rats, we studied the correlation between AVP action on the MAL and maximal urinary concentration. AVP (10(-6) M) significantly stimulated adenylate cyclase in MAL of H rats (7.4 +/- 0.9 to 43.8 +/- 4.6 fmol cAMP formed X 30 min-1 X mm-1, P less than 0.001) but not in CR rats (10.3 +/- 1.4 to 12.7 +/- 2.0 fmol cAMP formed X 30 min-1 X mm-1, NS). In contrast, AVP significantly stimulated adenylate cyclase of cortical, outer and inner medullary collecting tubules from both H and CR rats. Glucagon (10(-6) M) significantly stimulated adenylate cyclase of MAL from both H and CR rats. After 48 h of fluid deprivation, urinary osmolality was significantly higher (P less than 0.001) in the H (4,504 +/- 399 mosmol/kg H2O, n = 14) than CR (2,840 +/- 176 mosmol/kg H2O, n = rats. This observation was not attributable to differences in creatinine clearance (CR, 1.30 +/- 0.24; H, 1.24 +/- 0.03 ml/min, NS, n = 4) or plasma AVP (CR, 12.75 +/- 1.44; H, 12.38 +/- 1.17 pg/ml, NS, n = 6) levels. These results therefore suggest that the action of AVP on the MAL, in addition to the effect on collecting tubules, is involved in maximal urinary concentration in rats.
Effect of dietary NaCl on chloride uptake in rat collecting duct segment
Authors: Galla J. H. , Bonduris D. N. , Kirk K. A. , Luke R. G.
Published: December 2017

To explore further the mechanism of the effect of dietary NaCl intake on collecting duct (CDS) chloride uptake, we compared late distal chloride delivery to and urinary 36Cl recovery (the latter as an index of unidirectional efflux) from the CDS in four groups of male Sprague-Dawley rats. Groups were prepared for 7-10 days as follows: group 1, drinking 0.15 M NaCl; group 2A, regular diet; group 2B, regular diet plus deoxycorticosterone (2 mg im) (at 24 and 2 h before micropuncture); and group 3, low-NaCl diet. To increase tubule fluid flow rate and produce natriuresis without chloruresis, 0.15 M NaHCO3 at 5% body wt/h was infused in all groups except group 3, in which an infusion of 150 mM Na+, 55 mM Cl-, and 85 mM HCO3- was required to maintain a plasma chloride concentration equal to that in other groups. Plasma chloride concentration and arterial pH did not differ between groups before infusion. Urinary 36Cl recovery increased in parallel with dietary NaCl content (P = 0.0001). By analysis of multiple covariances, neither tubule fluid chloride concentration nor chloride delivery to the CDS correlated with urinary 36Cl recovery within any of the groups or for all animals studied. High doses of mineralocorticoid did not alter chloride uptake in group 2. These data suggest that progressive restriction of dietary NaCl enhances chloride uptake in the CDS of the rat unrelated to changes in plasma chloride concentration or chloride delivery from the superficial late distal tubules.
Microelectrode study of intracellular pH in frog skin: dependence on serosal chloride
Authors: Duffey M. E. , Kelepouris E. , Peterson-Yantorno K. , Civan M. M.
Published: December 2017

Replacement of external chloride has been known to reduce Na+ transport across whole frog skin. However, the sidedness and mechanism of the phenomenon have been unclear. In the present study, transepithelial current (IT), transepithelial resistance (RT), and basolateral membrane potential measured both with reference micropipettes (psi sc) and pH-selective microelectrodes (EscH) were monitored in isolated epithelial sheets from frog skin; removal of the underlying dermis facilitates ionic exchange across the basolateral membranes. The intracellular hydronium ion activity (acH) was 58 +/- 4 nM (means +/- SE) when the extracellular hydronium activity was 25 +/- 1 nM under base-line conditions. This measurement is equivalent to an intracellular pH (pHc) of 7.24 +/- 0.03 at an extracellular pH of 7.60 +/- 0.01, in reasonable agreement with estimates obtained by 31P- and 19F-nuclear magnetic resonance (NMR) analyses of frog skin. Complete replacement of mucosal Cl- by gluconate had variable effects on tissue current and resistance from preparation to preparation. The same ionic substitution on the serosal side uniformly produced a prompt reversible decrease in IT, increase in RT, and a substantial membrane depolarization of the short-circuited skins. In most of the preparations, the depolarization was preceded by a small hyperpolarization of 0.5-3.5 mV. The replacement of serosal Cl- also produced a fall in intracellular hydronium ion activity of 33 +/- 10 nM.The present date are consistent with the concept that serosal replacement of Cl- alkalinizes the cells by either favoring HCO3- entry or blocking HCO3- exit through a Cl- HCO3 antiport at the basolateral membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
In vitro effects of angiotensin II on glomerular function
Authors: Savin V. J.
Published: December 2017

Effects of incubation with angiotensin II (ANG II) on isolated rat glomeruli were studied to test the hypothesis that ANG II exerts a direct effect on glomerular ultrafiltration coefficient (Kf) or hydraulic conductivity (Lp). Glomeruli of adult Munich-Wistar rats were isolated in isotonic medium and incubated at 37 degrees C in control medium or in medium containing ANG II (5.3 X 10(-9) to 5.3 X 10(-6) M) for 20 min. Glomerular volume decreased after incubation with ANG II. Relative volume decrement of unselected cortical glomeruli averaged 6 +/- 3% in 5.3 X 10(-9) or 10(-8) M ANG II and 13 +/- 3% in 5.3 X 10(-6) M ANG II; volume of superficial cortical glomeruli and deep cortical glomeruli diminished by 9 +/- 2 and 5 +/- 0.5%, respectively, after incubation with ANG II 5.3 X 10(-6) M. Glomerular oncometric response after equilibration with media of differing protein concentrations was not altered by ANG II incubation. Kf and Lp assessed in samples of glomeruli following ANG II incubation averaged 4.5 +/- 0.5 nl X mm-1 X mmHg and 2.7 +/- 0.5 microliter X mm-1 X mmHg X cm2, respectively, and were not significantly different from control values (3.8 +/- 0.3 nl X mm-1 X mmHg and 2.4 +/- 0.3 microliter X mm-1 X mmHg X cm2, respectively. In replicate studies of individual glomeruli prior to and after ANG II incubation, Kf was also not significantly altered (control Kf, 6.1 +/- 1.1; Kf after ANG II, 4.4 +/- 0.9 nl X min-1 X mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)
Calcium transport across the pars recta of cortical segment 2 proximal tubules
Authors: Bourdeau J. E.
Published: December 2017

Partes rectae of cortical segment 2 proximal tubules were dissected from rabbit kidneys and perfused in vitro. Ca concentrations of perfused and collected fluids were measured by continuous-flow microcolorimetry. Epithelial Ca permeability (P) was estimated from the bath-to-lumen movement of 45Ca. The transepithelial voltage (psi) and [Ca2+] difference were varied simultaneously by changing perfusate composition. Tubules that were perfused and bathed with an identical artificial ultrafiltrate of plasma displayed a lumen-negative psi, a collectate [Ca] greater than perfusate, and net Ca secretion. Tubules perfused with "late" proximal tubule fluid (high [Cl], low [HCO3], low concentrations of Na+-cotransported solutes) demonstrated a lumen-positive psi, a perfusate [Ca2+] greater than the bath, a collectate [Ca] less than perfusate, and net Ca absorption. Under each of these conditions, net Ca flux was in the direction predicted by the experimentally measured driving forces for diffusional Ca transport. Tubules that were cooled while being perfused with late proximal tubule fluid showed an increased lumen-positive psi but reduced net Ca absorption. The latter finding was consistent with reduced Ca ion diffusion related to a smaller P at the lower temperature. I conclude that Ca2+ diffusion is an important component of net Ca absorption in this segment of the nephron.
Effects of gluco- and antiglucocorticoids on renal and aortic prostaglandin synthesis
Authors: Grunfeld J. P. , Eloy L. , Araujo A. , Russo-Marie F.
Published: December 2017

The effects of glucocorticoid agonists RU 26988 (G) and dexamethasone (D) and antagonist RU 486 (AG) on aortic and renal prostaglandin (PG) production were studied in Wistar rats. Blood pressure increased in rats administered G (20 mg X kg-1 X day-1) during 1 or 3 days; such increase was prevented by AG (100 mg X kg-1 X day-1). Renal papillary PGE2 release was increased after a 3-day administration of G, and this was prevented by AG. Neither G nor AG altered basal 6-keto-PGF1 alpha aortic production. However, G inhibited and AG magnified the stimulatory effect of ionophore A 23187, added in vitro, on 6-keto-PGF1 alpha production; AG reversed G inhibition. In addition, AG alone (20 mg X kg-1 X day-1 X 3 days) enhanced the stimulatory effect of angiotensin II (10(-8) M), added in vitro, on 6-keto-PGF1 alpha release. In vitro studies were performed on renomedullary interstitial cells grown in culture; G and D depressed PGE2 production in a dose-dependent manner; AG at equimolar 10(-8) M concentration inhibited this effect. In conclusion, AG inhibits the effects of G on blood pressure and PG synthesis. G exerts strong depressor activity on in vitro PGE2 renal production, whereas in vivo effects are more complex. Endogenous G inhibits aortic prostacyclin production, an action unmasked by AG administration. Diminished stimulation of vascular prostacyclin synthesis may contribute to vascular hyperreactivity in G-induced hypertension.
Fluctuations in intracellular pH associated with vasopressin stimulation
Authors: Brem A. S. , Pacholski M. , Lawler R. G.
Published: December 2017

Intracellular pH (pHi) was estimated in paired hemibladders isolated from Dominican toads (Bufo marinus) by the tissue distribution of [14C]5,5'-dimethyl-2,4-oxazolidinedione and [3H]inulin. Tissues were incubated with isotopes for 30 min to correlate changes in pHi with the approximate time of peak vasopressin (VP)-induced water flow. At serosal pH 7.1 in the presence of an osmotic gradient, the intracellular hydrogen ion concentration [( H+]i) after 30 min of VP (20 mU/ml) stimulation was 8.29 +/- 0.23 X 10(-8) M (pHi 7.08) compared with 5.19 +/- 0.46 X 10(-8) M (pHi 7.28) in unstimulated paired controls (n = 5, P less than 0.001). The cyclic AMP (cAMP) analogue 8-(p-chlorophenylthio)-cAMP (10(-5) M) mimicked the VP effects. A similar change was observed at serosal bath pH 8.2, where [H+]i was 1.67 +/- 0.06 X 10(-8) M (pHi 7.78) with VP vs. 1.11 +/- 0.04 X 10(-8) M (pHi 7.95) in matched controls (n = 8, P less than 0.001). In all cases, the hydroosmotic response was associated with a significant decrease in inulin space. When the osmotic gradient was eliminated with Ringer solution or isotonic sorbitol in the mucosal bath, VP produced a smaller decrease in pHi (approximately 0.08 pH units) at both serosal pH. 31P-nuclear magnetic resonance spectra showed a similar downward trend in pHi with cell swelling. When vasopressin was removed from the bath, pHi and inulin space in stimulated hemibladders returned to pretreatment values within 30 min, and the tissues were again capable of a maximum hydroosmotic response if rechallenged with the hormone.(ABSTRACT TRUNCATED AT 250 WORDS)
Mechanism of potassium depletion during chronic metabolic acidosis in the rat
Authors: Scandling J. D. , Ornt D. B.
Published: December 2017

Pair-fed rats on a normal K diet were given either 1.5% NH4Cl or water for 4 days. The acid-fed animals developed metabolic acidosis, negative K balance, and K depletion. Urinary Na excretion and urinary flow were not different between the groups beyond the first day. After the 4 days, isolated kidneys from animals in each of these groups were perfused at normal pH and bicarbonate concentrations. Urinary K excretion was similar between the groups despite the potassium depletion in the acid-fed animals. In contrast, isolated kidneys from animals with comparable K depletion induced by dietary K restriction readily conserved K (fractional excretion 0.35 +/- 0.04 vs. 0.83 +/- 0.09 by the kidneys from acid-fed animals, P less than 0.01). Sodium excretion and urinary flow were similar among the three groups of isolated kidneys. Plasma aldosterone concentrations were greater in the acid-fed rats after the 4 days of NH4Cl ingestion than in the control animals (43 +/- 10 vs. 10 +/- 2 ng/dl, P less than 0.01). Adrenalectomized rats were treated with either normal (4 micrograms/day) or high (22 micrograms/day) aldosterone replacement while ingesting NH4Cl for 4 days. Only in the presence of high aldosterone replacement did the acid-fed adrenalectomized animals develop K depletion. We conclude that chronic metabolic acidosis stimulates aldosterone secretion, and that aldosterone maintains the inappropriately high urinary potassium excretion and K depletion seen in this acid-base disorder.
Immunological segmentation of the rabbit distal, connecting, and collecting tubules
Authors: Poujeol P. , Ronco P. , Tauc M. , Geniteau M. , Chatelet F. , Sahali D. , Vandewalle A. , Verroust P.
Published: December 2017

To obtain monoclonal antibodies (MAB) specific for the different cell types of distal and collecting tubules, BALB/c mice were immunized with cell suspensions highly enriched in cells from the distal segments of the rabbit nephron. Nine MAB were selected and cloned. Four groups could be identified on the basis of double-labeling immunofluorescence (IF) on frozen kidney sections and on microdissected tubules. In addition, binding specificity at the cellular level was studied by immunoelectronmicroscopy (IEM) for selected MAB. A single MAB (group 1) was specific for distal bright cells and a subpopulation of cortical ascending limb cells. Six MAB (group 2) reacted with connecting and collecting tubules. Five of these (group 2A) had similar binding patterns and reacted identically with the two tubular segments. The MAB studied by IEM was specific for connecting and principal cells. One antibody (group 2B) reacted with only a fraction of the cells associated with the connecting tubule (CNT), but with all cells of the cortical collecting tubule (CCT). By IEM, this antibody was found to be specific for intercalated cells in CNT and bound both principal and intercalated cells of the CCT. Two MAB (group 3) reacted with antigen(s) expressed by the various terminal segments of renal tubule. MAB of groups 1 and 2A, which define distal bright cells and connecting-principal cells from the CNT-CCT, respectively, were used for cell fractionation experiments. Heterogeneous rabbit cortical cells were first incubated with the selected MAB. MAB-bearing renal cells were separated on plastic dishes previously coated with an affinity-purified goat anti-mouse immunoglobulin. Using these procedures it was possible to obtain highly purified subpopulations of distal, bright, or connecting-principal cells.
Plasma glutamine and renal ammoniagenesis in dogs with chronic metabolic acidosis
Authors: Halperin M. L. , Bun-Chen C.
Published: December 2017

The purpose of this investigation was to determine whether the rate of glutamine metabolism in the kidneys of normal dogs and dogs with chronic metabolic acidosis was influenced by the plasma glutamine concentration. Because glutamine is a major renal energy fuel, results were examined at a constant rate of energy or ATP turnover [i.e., per 100 ml glomerular filtration rate (GFR)]. Glutamine extraction per 100 ml GFR was directly proportional to the filtered load of glutamine in normal and acidotic dogs. The slope depicting this relationship was parallel to the filtered load of glutamine; however, in normal dogs it was lower and in acidotic dogs it exceeded the filtered load by approximately 22 mumol/100 ml GFR. With respect to the fate of the nitrogens of the glutamine extracted, alanine and ammonium were produced in normal dogs at a rate nearly equivalent to that of glutamine extracted, whereas ammonium production was almost twofold greater than the rate of glutamine extraction during acidosis. There was a relatively small but constant alanine release over the entire range of plasma glutamine concentrations in these dogs. Furthermore, infusion of glutamine to raise the plasma glutamine concentration twofold during acidosis resulted in an increased rate of glutamine extraction and ammonium production equal to that predicted from the increase in filtered load of glutamine. Therefore, variations of circulating glutamine concentration within the physiological range seem to have an important influence on the steady-state rate of renal glutamine metabolism in normal dogs and in dogs with chronic metabolic acidosis.
Cholera toxin enhances adenylate cyclase-dependent transport in toad urinary bladder
Authors: Hoch B. S. , Levine S. D.
Published: December 2017

Cholera toxin (CT) irreversibly ADP-ribosylates and activates the nucleotide-stimulatory (Ns) subunit of adenylate cyclase in many tissues, thereby eliciting cyclase-dependent functions. Although earlier studies performed at room temperature could not demonstrate CT-stimulated water transport in toad urinary bladder, subsequent work in other tissues has emphasized the need for incubation at 35-37 degrees C to effect ribosylation and the subsequent physiological effects. We found that incubating tissues with amphibian culture media, rather than Ringer solution, maintained tissue viability at this higher temperature and permitted prolonged incubation with CT. At 37 degrees C, in the presence of 0.1 mM phosphodiesterase inhibitor (1-methyl-3-isobutylxanthine, MIX), 0.2-200 nM mucosal CT caused a dose-dependent but submaximal enhancement of water flux and urea transport. Elimination of MIX from the bath diminished subsequent CT-induced stimulation, supporting a role for adenosine 3',5'-cyclic monophosphate (cAMP) as mediator of the CT effect. The increased water flow was stable for greater than 1 h after removal of CT from the bath, consistent with irreversible stimulation of the cyclase. Mucosal CT stimulated transport to a greater degree than serosal CT, paralleling the pattern seen in the intestine, which is compatible with passage of the toxin's a subunit across the cell to the serosal membrane cyclase. Exposure of the tissue's mucosal surface to GM1 ganglioside, (the natural receptor for the CT b subunit) yielded maximal stimulation of water flow and near-maximal urea transport, presumably by increasing CT's binding to the cell membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
Volume regulatory loss of Na, Cl, and K from rat brain during acute hyponatremia
Authors: Melton J. E. , Patlak C. S. , Pettigrew K. D. , Cserr H. F.
Published: December 2017

This study quantitatively evaluates the contribution of tissue Na, Cl, and K loss to brain volume regulation during acute dilutional hyponatremia (DH) and examines the mechanism of Na loss. DH was produced in pentobarbital sodium-anesthetized rats by intraperitoneal infusion of distilled water and brain water and electrolytes analyzed 30 min, 1 h, 3 h, 4 h, or 6 h later. The rate of Na and Cl loss was greatest during the first 30 min of DH (0.43 and 0.47 meq X kg tissue dry wt-1 X min-1, respectively). Net loss of Na and Cl was maximal after 3 h of DH. K loss was slower, achieving significance after 3 h. Electrolyte loss was sufficient to account for observed brain volume regulation after three or more hours of DH. Measurements of 22Na influx and efflux across the blood-brain barrier showed that barrier permeability to Na is unchanged during DH. Analysis of results using a two-compartment model of plasma-brain exchange suggests that loss of brain Na during DH does not result solely from a shift of electrolyte across the blood-brain barrier to plasma, and thus provides indirect evidence for an additional pathway for Na loss, presumably via cerebrospinal fluid.
Atrial natriuretic factor inhibits maximal tubuloglomerular feedback response
Authors: Huang C. L. , Cogan M. G.
Published: December 2017

The effect of atrial natriuretic factor (ANF) on maximal tubuloglomerular feedback was assessed in 16 Munich-Wistar rats. When the loop of Henle was not perfused, ANF increased single nephron glomerular filtration rate (SNGFR) and stop-flow pressure (SFP) from 32 +/- 2 nl/min and 32 +/- 2 mmHg in the control period to 37 +/- 2 nl/min (P less than 0.05) and 40 +/- 2 mmHg (P less than 0.025) after ANF administration, respectively. Because ANF caused SFP to rise but did not significantly alter plasma protein concentration, the estimated glomerular capillary hydraulic pressure increased. Maximal tubuloglomerular feedback response (examined by increasing orthograde microperfusion of the loop from 0 to 50 nl/min) was significantly inhibited by ANF; changes in SNGFR and SFP during the control state, -9 +/- 2 nl/min and -9 +/- 1 mmHg, were reduced to -4 +/- 2 nl/min (P less than 0.05) and -5 +/- 1 mmHg (P less than 0.05), respectively, after ANF administration. In conclusion, the increase in SNGFR caused by ANF is associated with an increase in glomerular capillary hydraulic pressure and with a blunted maximal tubuloglomerular feedback response.
Localization of alpha 2-adrenoceptor-mediated increase in renal Na+, K+, and water excretion
Authors: Stanton B. , Puglisi E. , Gellai M.
Published: December 2017

Free-flow micropuncture and clearance studies were conducted in male Sprague-Dawley rats to investigate the effects of alpha 2-adrenoceptor stimulation on Na+, K+, and water transport along the nephron. Intravenous infusion of the selective alpha 2-adrenoceptor agonist B-HT 933 at 1 mg X kg-1 X h-1 increased urinary flow rate from 16.2 +/- 3.6 to 84.8 +/- 11.9 microliter/min, fractional excretion of Na+ from 1.36 +/- 0.31 to 3.57 +/- 0.52%, and fractional excretion of K+ from 26.9 +/- 3.0 to 42.3 +/- 2.2%, The diuresis, saluresis, and kaliuresis were not the result of increases in glomerular filtration rate or mean arterial blood pressure. Urine osmolality decreased from 1,126 +/- 177 to 325 +/- 33 mosmol/kg water and in 8 of the 11 animals studied B-HT 933 decreased urine osmolality to hyposmotic levels, suggesting a possible interaction between the alpha 2-adrenoceptor agonist and vasopressin. The alpha 2-adrenoceptor antagonist yohimbine (0.25/mg bolus, iv) inhibited the diuresis, saliuresis, and kaliuresis. In micropuncture studies, B-HT 933 was without effect on single-nephron glomerular filtration rate or on Na+, K+, and water transport along the superficial proximal tubule, loop of Henle, or distal tubule. Thus stimulation of alpha 2-adrenoceptors increases Na+, K+, and water excretion by inhibiting tubule reabsorption of these substances at nephron sites beyond the superficial distal tubule, most likely by the collecting tubule.
Sex differences in function and distribution of alpha 1- and alpha 2-adrenoceptors in rabbit urethra
Authors: Morita T. , Latifpour J. , O'Hollaren B. , Wheeler M. A. , Weiss R. M.
Published: December 2017

To define the functional role of postsynaptic alpha-adrenoceptors in urethral smooth muscle, we examined the effects of various alpha-adrenergic agonists and antagonists on the contractile properties of the isolated urethra of male and female rabbits and quantified the population of alpha 1-and alpha 2-adrenoceptors, using radioligand receptor binding techniques. Norepinephrine (NE), epinephrine, and phenylephrine, an alpha 1-adrenergic agonist, induced increases in contractile force in both the male and female urethra. Clonidine, an alpha 2-adrenergic agonist, caused a relatively large contractile response in the female urethra but only a small contractile response in the male urethra. Receptor binding studies indicated that the male urethra contains almost equal amounts of alpha 1- and alpha 2-adrenoceptors (32 vs. 34 fmol/mg, respectively), whereas the female urethra contains a significantly greater density of alpha 2- than alpha 1-adrenoceptors (122 vs. 34 fmol/mg, respectively). Our studies indicate that both alpha 1- and alpha 2-adrenoceptors cause contractile responses in male and female rabbit urethra; and the greater response to alpha 2-agonist in female than male urethra is correlated with a higher density of alpha 2-adrenoceptors in this tissue.