bluuebunny/crossref_metadata_2025 huggingface dataset:
Anti-GBM antibody-induced proteinuria in isolated perfused rat kidney
Authors: Couser W. G. , Darby C. , Salant D. J. , Adler S. , Stilmant M. M. , Lowenstein L. M.
Published: December 2017

The effect of anti-GBM antibody on protein excretion was studied in isolated rat kidneys perfused with 20 mg of sheep anti-rat GBM (experimental) or nonantibody sheep IgG (control). Six control kidneys excreted 176 +/- 31 micrograms/min of BSA initially, rising to 296 +/- 111 micrograms/min at 2 h. Fractional clearance of BSA rose from 0.51 to 1.70%. Eight experimental kidneys excreted 211 +/- 56 micrograms/min of BSA, increasing to 1,924 +/- 804 micrograms/min at 2 h. Fractional BSA clearance increased from 0.56 to 11.49%. After 60 min, BSA excretion in anti-GBM-perfused kidneys exceeded controls by a factor of 6.5-7.9 (P less than 0.05) and fractional BSA clearance exceeded controls by a factor of 5.8-7.1 (P less than 0.05). Studies with fluorescent markers indicated proteinuria to be of glomerular origin in antibody-perfused kidneys. There were no significant differences between anti-GBM-perfused and control kidneys in perfusion pressures, perfusate flow rates, urine flow rates, inulin clearance, or sodium reabsorption. Antibody to GBM can induce a marked increase in glomerular permeability to BSA and IgG without participation of other systemic humoral or cellular mediation systems.
Effect of pentobarbital and hemorrhage on renal autoregulation
Authors: Kremser P. C. , Gewertz B. L.
Published: December 2017

Renal blood flow and hemodynamic autoregulation were assessed in seven chronically instrumented canines studied in the conscious state and after pentobarbital anesthesia administration (30 mg/kg). The effects of acute arterial hemorrhage (10 and 15 ml/kg) were also studied. In the conscious state, no significant changes in autoregulation were observed following 10 mg/kg hemorrhage. With pentobarbital and 10 ml/kg hemorrhage, a significant change in the limits of autoregulation was noted (autoregulatory limit 78.5 +/- 16.6 vs. 88.4 +/- 25.3 mmHg, P less than 0.05). Four animals were also studied in the conscious state following 15 ml/kg acute arterial hemorrhage. In these animals, mean arterial pressure decreased (from 105.0 +/- 11.4 to 87.8 +/- 7.2 mmHg, P less than 0.025) but renal blood flow (from 293 +/- 38 to 272 +/- 65 ml/min) and autoregulatory limit did not change. We conclude that renal blood flow is unaffected by hemorrhage or pentobarbital alone. In the conscious state, renal pressure-flow autoregulation is maintained despite moderate hemorrhage and systemic hypotension. The lower limit of autoregulation is significantly changed by even minor hemorrhage in the pentobarbital-anesthetized state.
Heteroporous model of glomerular size selectivity: application to normal and nephrotic humans
Authors: Deen W. M. , Bridges C. R. , Brenner B. M. , Myers B. D.
Published: December 2017

A heteroporous model of the glomerular filtration barrier was developed and used to interpret dextransieving data in healthy volunteers (normal controls), in patients with nephrotic range proteinuria (grouped as grades I-III, according to severity), and in a group of previously nephrotic patients whose proteinuria was in remission (“resolved controls”). Several hypothetical pore-size distributions were compared in terms of their ability to describe the selective increases in the fractional clearance of large dextrans observed with increasing severity of proteinuria. The most successful model examined was based on the assumption that the major portion of the capillary wall functions as an isoporous membrane, but that a small fraction of the filtrate passes through pores that are unable to discriminate among dextrans of different sizes. The value of the membrane parameter that reflects the relative importance of the nonselective pores was found to increase in parallel with the fractional clearance of immunoglobulin G; it increased progressively in going from normal controls to resolved controls to grades I-III nephrotics. The observed patterns of protein excretion could not, however, be explained entirely by a loss of glomerular size selectivity. Variations in membrane selectivity on the basis of molecular charge and/or molecular configuration are also likely to have been important.
Active transport and exchange diffusion of Cl across the isolated skin of Rana pipiens
Authors: Drewnowska K. , Biber T. U.
Published: December 2017

Transepithelial Cl influx and efflux were measured in pairs of frog skin (Rana pipiens) matched according to short-circuit current, tissue conductance, and transepithelial potential (TEP). The skins were bathed symmetrically in NaCl Ringer and voltage clamped at TEP values ranging from -60 to +60 mV. At 0 TEP, Cl influx and net inward Cl movement (in neq X h-1 X cm-2) were, respectively, 961 +/- 116 and 463 +/- 68 in NaCl Ringer, 509 +/- 52 and 202 +/- 53 in amiloride-treated skins, 4,168 +/- 777 and 1,444 +/- 447 in theophylline-treated skins, and 587 +/- 38 and 97 +/- 44 in Na-free Ringer. A correlation was discovered between short-circuit current and Cl fluxes corresponding to a 2:6:1 relationship between changes in active Na transport and active Cl transport. Deviations from the predicted Cl flux ratio indicate the presence of exchange diffusion in the range of spontaneously occurring TEPs, in contrast to observations on R. temporaria and R. esculenta. The experiments indicate that a substantial portion of transepithelial Cl movement proceeds transcellularly 1) via active Cl transport that is Na dependent, amiloride sensitive, stimulated by theophylline, and apparently correlated with active Na transport, and 2) by means of exchange diffusion that not only occurs under short-circuit conditions but also at positive TEPs. It is possible to explain both the exchange diffusion and the properties of active Cl transport by a Cl-HCO3 exchange system at the apical side of the transporting cell that interacts with a Na-H exchange mechanism, a notion consistent with the recent observation of an amiloride-induced decrease in intracellular pH.
Metabolic effects of sodium bicarbonate in hypoxic lactic acidosis in dogs
Authors: Graf H. , Leach W. , Arieff A. I.
Published: December 2017

The metabolic effects of NaHCO3 therapy in hypoxic lactic acidosis were evaluated in the anesthetized dog. Hypoxic lactic acidosis was induced by ventilating the dogs with a hypoxic gas mixture of 8% O2/92%N2, resulting in arterial PO2 of less than 30 mmHg, pH below 7.20, bicarbonate less than 12 mM, and lactate more than 7 mM. In this situation lactate accumulates because of overproduction of lactate by gut and carcass in the presence of a diminished capacity of the liver to extract lactate. After the development of hypoxic lactic acidosis the dogs were treated for 60 min with either NaHCO3 or NaCl or had no therapy. Sixty minutes of either treatment resulted in further declines of blood pH and bicarbonate that were similar in all three groups. NaHCO3-treated animals, however, showed an increase in blood lactate that were significantly higher than those treated with NaCl or those that had no therapy. This could be explained by a significantly higher gut lactate production with NaHCO3 therapy than in the NaCl-treated group. Concomitantly NaHCO3-treated animals showed a decrement in liver and gut blood flow that did not occur with NaCl treatment. Only NaHCO3 therapy was associated with a further decrease of liver intracellular pH, which could be attributed to both an increase in the CO2 load to the liver and increased tissue lactate levels, which were not observed with NaCl or no therapy. Additionally, liver lactate extraction was not improved by administration of NaHCO3 or NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)
Mechanism of bradykinin, ADH, and cAMP interaction in rabbit cortical collecting duct
Authors: Schuster V. L.
Published: December 2017

Vasopressin (ADH) and bradykinin (BK) have been shown to stimulate prostaglandin synthesis in rabbit cortical collecting tubules. We studied ADH and BK effects on osmotic water flow (Lp), Na transport (JNa), and transepithelial voltage (VT). Bath BK but not lumen BK blunted subsequent ADH hydroosmotic responses. This BK effect was prevented by ibuprofen or pertussigen pretreatment and was overcome with exogenous cAMP, suggesting that BK, via prostaglandins, interferes with ADH action on Lp at the cAMP generation step. In contrast, bath BK had no effect on bath-to-lumen (Jb-1Na) or lumen-to-bath (Jl-bNa) Na flux or on VT. As reported by others, ADH lowered Jl-bNa and depolarized VT; however, prostaglandin synthesis inhibitors neither prevented nor reversed these ADH effects. Together, these BK and ADH data do not support regulation of JNa by peptide-stimulated prostaglandins. Moreover, cAMP alone depolarized VT but had no effect on Jl-bNa. Therefore, ADH-induced depolarization of VT may at least partly owe to cAMP effects on VT independent of accompanying changes in JNa. As with Lp, bath BK blunted subsequent ADH effects on VT and, to a lesser extent, Jl-bNa; these BK effects on ADH action were also prevented by ibuprofen or pertussigen pretreatment. The data are consistent with the following model: 1) ADH depolarizes VT and increases Lp via cAMP; 2) ADH decreases JNa via neither cAMP nor prostaglandins; and 3) BK, via prostaglandins, inhibits the actions of ADH on Lp and VT at the inhibitory guanyl-nucleotide regulatory subunit of adenylate cyclase.
Segmental localization of the rabbit renal proximal tubular Na+-H+ exchange system
Authors: Kragh-Hansen U. , Roigaard-Petersen H. , Sheikh M. I.
Published: December 2017

The activity of the Na+-H+ exchanger in rabbit proximal tubule was investigated by using luminal membrane vesicles prepared from "outer cortex" (proximal convoluted tubule) or "outer medulla" (proximal straight tubule). The purity of the preparations was examined by measuring the activity of several marker enzymes, and the degree of cross-contamination and the functional state of the membrane vesicles were assessed by studying Na+-dependent uptake of D-glucose. The Na+ uptake by pars convoluta membrane vesicles exhibited an overshoot in the presence of an intravesicular greater than extravesicular H+ gradient. The overshoot was eliminated by omitting or reversing the transmembranal H+ gradient or by adding amiloride. In contrast, Na+ uptake by pars recta membrane vesicles did not show an overshoot and was independent of H+ gradients and of amiloride. However, Na+ uptake by pars recta membrane vesicles pretreated with monensin exhibited an overshoot. This overshoot apparently was amiloride insensitive. The findings propose that the Na+-H+ exchanger is predominantly operative in the proximal convoluted tubule and is either lacking or of minor significance in the proximal straight tubule.
Effects of metabolic acidosis, alkalosis, and dietary hydrogen ion intake on phosphate transport in the proximal convoluted tubule
Authors: Quamme G. A.
Published: December 2017

Early proximal convoluted tubules were perfused in vivo with equilibrium Ringer buffered at pH 7.65 and 6.5 to characterize phosphate absorption due to changes in extracellular and intracellular hydrogen ion concentration. Phosphate absorption is normally greater from intraluminal pH 7.65 compared with pH 6.5 in thyroparathyroidectomized rats with fractional phosphate excretion of 0.5%. Metabolic alkalosis produced by bicarbonate infusion in rats ingesting normal amounts of phosphate (45 mg/day) resulted in an increase in overall renal phosphate reabsorption (fractional phosphate excretion 0.3%). The Jmax and Km values were: pH 7.65, 33.67 +/- 13.49 pmol X min-1 X mm-1, and 1.74 +/- 0.30 mM; pH 6.5, 24.87 +/- 6.22 and 0.50 +/- 0.25, respectively. By contrast, rats on a high dietary phosphate intake (180 mg/day) demonstrated a large increase in urinary phosphate excretion (18%) following bicarbonate infusion, which was due to a decrease in tubular phosphate absorption from both alkaline and acidic luminal pH values. Acute metabolic acidosis did not significantly alter tubular transport at either intraluminal pH value. In contrast, rats maintained on an elevated dietary acid intake for 5 days had a phosphaturia (fractional excretion 7.1%) and diminished reabsorptive capacity. Dietary acidosis also decreased tubular phosphate transport in rats previously maintained on phosphate-restricted diets. These data suggest that acid-base balance may modulate tubular phosphate transport independent of intraluminal pH and phosphate concentration. Further, these changes depend on the chronicity of exposure and act independent but integral to the effects of parathyroid hormone and the intrinsic adaptation to dietary phosphate availability.
Effect of urinary alkalinization on the intrarenal formation of kinins
Authors: Brukman J. , Murray R. D. , Churchill P. C. , Scicli A. G. , Carretero O. A.
Published: December 2017

Alterations in the urinary excretion rate of kallikrein (UKKV) have frequently been assumed to reflect alterations in the intrarenal generation of kinins. Since other factors such as urinary pH and the activity of renal kininases may affect the intrarenal concentration of kinins, we investigated the effect of urinary alkalinization on kinin excretion in the presence and absence of kininase II inhibition. Urine was collected from the ureters of rats during control (ctl) (0.15 M NaCl infusion) and experimental (exp) periods. During exp periods, group I (time control) was infused with 0.15 M NaCl, group II with 0.3 M NaCl, and groups III and IV with 0.3 M NaHCO3, all at 0.12 ml/min. Prior to the ctl period, group IV was pretreated with the kininase II inhibitor captopril (40 mg/kg). During the exp period, urinary kinin excretion (UKiV) increased significantly in all groups ([exp - ctl] UKiV = 21 +/- 7, 27 +/- 9, 52 +/- 14, and 70 +/- 9 pg X min-1 X kg-1 in groups I, II, III, and IV, respectively). Urinary pH increased significantly in groups II, III, and IV. The increases in UKiV and pH were significantly greater in the bicarbonate-infused rats than in control. Partial correlation coefficients show that UKiV correlates with a high degree of significance only with urinary pH (r = 0.6). During the ctl period, UKiV in the captopril-pretreated rats was not different from that in other groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Na-K-ATPase in nephron segments of rats developing spontaneous hypertension
Authors: Garg L. C. , Narang N. , McArdle S.
Published: December 2017

Na-K-ATPase activity was determined in seven specific nephron segments of 5- and 12-wk-old spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) controls. The enzyme activity in proximal convoluted tubule (PCT) and proximal straight tubule (PST) was significantly higher in 5-wk-old SHR than in WKY. However, Na-K-ATPase activity in medullary thick ascending limb (MTAL), cortical thick ascending limb (CTAL), and distal convoluted tubule (DCT) was significantly lower in 5-wk-old SHR than in WKY. There were no significant differences in the enzyme activity in PCT, PST, MTAL, CTAL, and DCT in 12-wk-old SHR and WKY. Furthermore, there were no significant differences in Na-K-ATPase activity in collecting duct segments of 5- or 12-wk-old SHR and age-matched WKY. The possible role of the abnormal pattern of Na-K-ATPase activity in PCT, PST, MTAL, CTAL, and DCT in 5-wk-old SHR in generation of hypertension in this strain remains to be determined.
Effects of calcium on the vasopressin-sensitive cAMP metabolism in medullary tubules
Authors: Kusano E. , Murayama N. , Werness J. L. , Christensen S. , Homma S. , Yusufi A. N. , Dousa T. P.
Published: December 2017

The modulatory effect of Ca on [Arg8]vasopressin-dependent (AVP) cAMP metabolism was studied in medullary collecting tubules (MCT) and medullary ascending limbs (MAL) microdissected from rat kidney. In MCT segments incubated in vitro with AVP, the accumulation of cAMP was enhanced (delta +59%) when Ca was omitted from the incubation medium compared with a medium with 2 mM of ionized calcium (Ca2+). Ionophore A23187 caused a decrease in AVP-stimulated cAMP accumulation in MCT in the presence of 2 mM Ca2+ but not in a Ca2+-free medium. Diltiazem and verapamil enhanced the AVP-stimulated cAMP accumulation in MCT; PTH had no detectable effect. A23187 caused a dose-dependent inhibition of cAMP accumulation stimulated by AVP with forskolin in both MCT and in MAL. However, in MAL the A23187 concentration needed for half-maximum inhibition (6.3 X 10(-6) M) was higher than for MCT (3.9 X 10(-7) M). The maximum inhibition in MAL (-65%) was less than in MCT (-97%). In the presence of 3-isobutyl-1-methylxanthine, AVP-stimulated cAMP accumulation was inhibited by A23187 in MCT (-45%) but not in MAL. Naproxen or ibuprofen did not relieve the inhibitory action of A23187 in MCT. Added Ca2+ inhibited the AVP-stimulated adenylate cyclase in MCT and MAL (half-maximum approximately equal to 5 X 10(-4) M Ca2+) and stimulated cAMP phosphodiesterase (cAMP-PDIE) in both MCT and in MAL (half-maximum approximately equal to 9 X 10(-5) M Ca2+). Incubation of MCT and MAL with A23187 decreased (-50%) the content of ATP. Results suggest that increased influx of extracellular Ca2+ inhibits the AVP-stimulated cAMP accumulation in MCT and to a much lesser degree in MAL. Deceased cAMP accumulation in MCT is probably due to both stimulation of cAMP-PDIE and the inhibition of adenylate cyclase, whereas in MAL it is due to stimulation of cAMP-PDIE. The results suggest that Ca2+ influx exhibits a negative modulatory effect on AVP-dependent cAMP metabolism mainly in MCT.
Effects of ouabain on autoregulation of renal blood flow in dogs
Authors: Tamaki T. , Fukui K. , Fujioka S. , Iwao H. , Okahara T. , Abe Y.
Published: December 2017

Effects of ouabain on the autoregulation of renal blood flow (RBF) and renin release were examined in filtering and nonfiltering kidneys of anesthetized dogs. Autoregulation of RBF was observed in both kidneys; however, autoregulation in the nonfiltering kidney was comparatively less efficient. These findings indicate that both the myogenic mechanism via a sensor element in the afferent arteriole, a so-called baroreceptor, and the tubuloglomerular feedback mechanism via the macula densa are essential for complete autoregulation. In both the control and nonfiltering kidney, intrarenal arterial infusion of ouabain abolished the autoregulation of RBF and glomerular filtration rate, with no change in the renal vascular sensitivity to vasoactive substances or in renin release induced by pressure reduction. Since various vasoactive drugs elicited a normal vascular response, it appears that the site of action of ouabain was not the vascular contractile elements; at least, an impairment of autoregulation during ouabain infusion was apparently not due to a defect in these elements. These results suggest the possible existence of another mediator, a sensor element in the afferent arteriole that is affected by ouabain. Ouabain may abolish the autoregulation of RBF and renin release via a modification of this baroreceptor in the afferent arteriole as well as through inhibition of the macula densa.
Effect of buffer infusion during acute respiratory acidosis
Authors: Bengele H. H. , Schwartz J. H. , McNamara E. R. , Alexander E. A.
Published: December 2017

We previously reported that acute respiratory acidosis (ARA) did not stimulate inner medullary collecting duct (IMCD) acidification. It was possible that the failure to find enhanced IMCD acidification was a function of insufficient buffer delivery. To answer this question we studied IMCD acidification in rats with ARA during the infusion of the buffer creatinine. We employed the microcatheterization technique to directly measure pH and PCO2 with glass membrane electrodes and also obtained fluid samples for the measurement of titratable acid and ammonium. Arterial pH was 7.19 +/- 0.01 and PCO2 was 93 +/- 2 mmHg. The IMCD data were analyzed as a function of IMCD length (approximately 6 mm). Equilibrium pH decreased from 5.99 +/- 0.05 to 5.58 +/- 0.02 and PCO2 increased from 71 +/- 11 to 132 +/- 6 mmHg between origin and tip. Bicarbonate delivery decreased from 111 +/- 14 to 38 +/- 2 nmol/min; titratable acid increased from 867 +/- 87 to 1,625 +/- 61 nmol/min, but ammonium delivery did not change along the duct. Thus, estimated net acid increased from 1,772 +/- 155 to 2,709 +/- 88 nmol/min. We conclude that during the presence of increased buffer delivery to the IMCD, rats with ARA markedly increased proton secretion along the terminal nephron.
Neurogenic regulation of proximal bicarbonate and chloride reabsorption
Authors: Cogan M. G.
Published: December 2017

Although a change in renal nerve activity is known to alter proximal reabsorption, it is unclear whether reabsorption of NaHCO3 or NaCl or both are affected. Sprague-Dawley rats (n = 10) were studied using free-flow micropuncture techniques during euvolemia and following acute ipsilateral denervation. Glomerular filtration rate and single nephron glomerular filtration rate were stable. Absolute proximal bicarbonate reabsorption fell following denervation (933 +/- 40 to 817 +/- 30 pmol/min) with a parallel reduction in chloride reabsorption (1,643 +/- 116 to 1,341 +/- 129 peq/min). Urinary sodium, potassium, bicarbonate, and chloride excretion all increased significantly. To further assess the physiological significance of neurogenic modulation of proximal transport, other rats (n = 6) were subjected to acute unilateral nephrectomy (AUN). There is evidence that AUN induces a contralateral natriuresis (renorenal reflex) at least partially by causing inhibition of efferent renal nerve traffic. AUN caused significant changes in proximal NaHCO3 and NaCl reabsorption as well as in whole kidney electrolyte excretion in the same pattern as had denervation. Prior denervation of the remaining kidney prevented the proximal and whole kidney response to AUN (n = 6). In conclusion, depression of renal nerve activity inhibits both NaHCO3 and NaCl reabsorption in the rat superficial proximal convoluted tubule. The data are consistent with the hypothesis that changes in renal nerve activity modify whole kidney electrolyte excretion under physiological conditions at least partially by regulating proximal transport.
Indirect immunoselection of late distal cell populations from rabbit kidney cortex
Authors: Vandewalle A. , Tauc M. , Cluzeaud F. , Ronco P. , Chatelet F. , Verroust P. , Poujeol P.
Published: December 2017

This study describes a method for the separation of distal cell populations based on the sequestration of proximal cells on immunoadsorbent columns (CNBr-activated Sepharose 6MB) bound with three brush-border monoclonal antibodies (S6-Mab). A high yield of isolated cell suspension from rabbit kidney cortex was prepared by mechanical dissociation after perfusion and incubation of the kidneys with 10(-3) M EDTA. The sequestration of the proximal cells was achieved in two sequential chromatographic steps. About 92% of the applied cells were first retained on an S6-Mab column after a 60-min stationary stage and the unbound cells were submitted by direct flow to a second S6-Mab column. In such conditions, 8 X 10(6) cells were recovered when starting with 331 X 10(6) cortical cells. The efficiency of the proximal cell depletion process was confirmed by an 80% decrease in brush-border enzymes, a very low phosphoenolpyruvate carboxykinase activity, and absence of cells bearing long microvilli, as ascertained by electron microscopy. This immunodepleted cell population presented the enzymatical characteristics of cells from the more distal segments. As compared with the initial cell suspension, these cells exhibited higher hexokinase (2.3 times), succinate dehydrogenase (1.5 times), and Na+-K+-ATPase (2.6 times) activities. In addition, adenylate cyclase activities remained sensitive to parathormone, arginine vasopressin, and isoproterenol. The functional capacity of these immunodepleted cells was assessed by an almost complete exclusion of eosin dye, a low Na+ and high K+ intracellular content, and a high respiratory rate of oxygen consumption. In conclusion, this immunoselective process makes it possible to obtain subpopulations of renal cortical cells possessing the main characteristics of the distal, connecting, and collecting cells for physiological and metabolic studies.
Phorbol ester-induced alkalinization of canine renal proximal tubular cells
Authors: Mellas J. , Hammerman M. R.
Published: December 2017

To determine whether exposure of renal proximal tubular cells to tumor-promoting phorbol esters results in intracellular alkalinization, we incubated suspensions of proximal tubular segments isolated from dog kidney with these compounds. Changes in intracellular pH were detected by measurements of the distribution of [14C]5,5-dimethoxazolidine-2-4-dione (DMO). Incubations of segments with 10(-6) M of the tumor-promoting phorbol esters phorbol-12,13-dibutyrate or 12-O-tetradecanoylphorbol-13-acetate (TPA), under conditions such that extracellular [Na+] greater than intracellular [Na+], effected intracellular alkalinization detectable within 1-2 min. Incubation with the inactive phorbol ester 4 alpha-phorbol did not. Incubation with as little as 10(-10) M phorbol-12,13-dibutyrate effected intracellular alkalinization. Incubation with 10(-12) M phorbol-12,13-dibutyrate did not. Alkalinization was not observed under conditions such that extracellular [Na+] = intracellular [Na+]. Alkalinization could be prevented by inclusion of 10(-3) M amiloride in incubations. Our findings are consistent with an action of tumor-promoting phorbol esters to stimulate Na+-H+ exchange across the plasma membrane of the renal proximal tubular cell. It is possible that the stimulation reflects a mechanism by which hormones and/or growth factors exert actions in proximal tubule.
Increased transport of inorganic phosphate in renal brush borders of spontaneously hypertensive rats
Authors: Bindels R. J. , Geertsen J. A. , Van Os C. H.
Published: December 2017

Phosphate metabolism was studied in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) by measuring serum phosphate concentrations and 24-h urinary phosphate excretions in rats placed in metabolic cages from 6 to 23 wk of age. Serum phosphate concentrations in SHR were significantly lower than those in WKY at 6, 12, and 20 wk of age. In addition, 24-h urinary phosphate excretion was lower in SHR relative to WKY from 6 through 23 wk of age. The hypophosphaturia in SHR was accompanied with an increase in the maximal transport rate of Na+-dependent phosphate transport in renal brush border membrane vesicles (BBMV) isolated from kidney cortex at 6, 12, and 20 wk of age. The apparent affinity for phosphate did not differ significantly between WKY and SHR at all ages studied. A direct relationship between maximal Na+-dependent phosphate transport rates in BBMV and serum phosphate concentrations was observed in both strains. In SHR, phosphate homeostasis is disturbed from 6 wk of age on.
Microperfusion study of proximal tubule bicarbonate transport in maleic acid-induced renal tubular acidosis
Authors: Bank N. , Aynedjian H. S. , Mutz B. F.
Published: December 2017

Microperfusion studies were carried out in rats to examine the abnormality in proximal tubule HCO3- transport caused by maleic acid administration. Permeability of the proximal tubule to HCO-3 was measured by perfusing proximal tubules with a HCO3- -free low-buffer isotonic equilibrium solution containing acetazolamide after plasma [HCO3-] had been raised by intravenous NaHCO3 infusion. Insulin recovery in the collected perfusate was approximately 100% in control and maleic acid-treated rats. CO2 influx measured by microcalorimetry was not significantly different in control vs. maleic acid-treated rats. Thus maleic acid did not cause increased permeability of the proximal tubule to either inulin or HCO3-. In a second group of experiments, proximal tubule fluid and HCO3- efflux were measured in paired-reperfusion experiments before and after maleic acid administration. The perfusion fluid contained 25 mM HCO3- and 120 mM Cl-. HCO3- absorption was inhibited 25% (79 pmol/min), Na+ was inhibited 22% (164 pmol/min), and Cl- absorption (calculated as the anion gap) by 85 pmol/min. [HCO3-] in the collected perfusate rose significantly after maleic acid, presumably accompanied by a fall in [Cl-]. The observations indicate that proximal renal tubular acidosis (RTA) induced by maleic acid is characterized by impaired lumen-to-blood transport of sodium bicarbonate and chloride but not by increased backflux. Based on previously demonstrated effects of maleic acid on mitochondrial energy metabolism and cellular ATP levels, we postulate that the principal transport abnormality is impaired basolateral membrane active sodium transport, leading to a secondary reduction in brush border Na+-H+ exchange.(ABSTRACT TRUNCATED AT 250 WORDS)
In vitro autoradiographic localization of ANP receptors in rat kidney and adrenal gland
Authors: Chai S. Y. , Sexton P. M. , Allen A. M. , Figdor R. , Mendelsohn F. A.
Published: December 2017

The radioligand 125I-ANP-(99-126) was used to map receptors for atrial natriuretic peptide (ANP) in the rat kidney and adrenal gland using in vitro autoradiography and computerized densitometry. In the kidney a very high density of receptors was found overlying glomeruli; these sites had a binding affinity constant of 0.48 +/- 0.06 X 10(-9) M-1 and a site concentration 818 +/- 108 fmol X mg protein-1. A moderate density of receptors was seen in the inner renal medulla; these sites had a binding constant of 0.9 +/- 0.2 X 10(9) M-1 and a receptor concentration of 204 +/- 44 fmol X mg protein-1, and moderate receptor density was also seen in the inner stripe of the outer medulla overlying vasa recta bundles. Diffuse low-density binding was also detected in the outer cortex. In all cases these patterns were abolished by 1 micron ANP-(101-126) or 1 microM atriopeptin III but not by a range of unrelated peptides. In the adrenal, a high density of binding was found overlying the zona glomerulosa, whereas a moderate density occurred in the zona fasciculata. Binding was not detected in the adrenal medulla. These results provide evidence for several classes of ANP receptor distribution in kidney and adrenal and suggest multiple roles of the peptide in fluid and electrolyte homeostasis.
Glucocorticoids and metabolic acidosis-induced renal transports of inorganic phosphate, calcium, and NH4
Authors: Boross M. , Kinsella J. , Cheng L. , Sacktor B.
Published: December 2017

The initial rate (5 s) of Na+-dependent inorganic phosphate (Pi) uptake in brush-border membrane vesicles isolated from rat proximal tubule was decreased in metabolic acidosis, 0.42 +/- 0.02 vs. 0.59 +/- 0.05 nmol/mg protein, in vesicles from control animals. Phosphate, ammonium, and Ca2+ excretions were increased 100, 600, and 56%, respectively. These changes in brush-border Pi transport and urinary excretion of ions were largely dependent on intact adrenal glands. After adrenalectomy there were no significant changes in brush-border Pi transport, Pi, and Ca2+ excretion, whereas ammonium excretion increased only 300% compared with controls. When the glucocorticoid dexamethasone was administered to adrenalectomized animals, it mimicked the effects of metabolic acidosis both in the presence and the absence of metabolic acidosis. The initial rate of brush-border Pi transport was decreased by dexamethasone administration to 0.37 +/- 0.04 nmol/mg protein in adrenalectomized acidotic animals and 0.39 +/- 0.03 nmol/mg protein in adrenalectomized animals. Dexamethasone administered to adrenalectomized acidotic animals increased Pi, ammonium, and Ca2+ excretion 190, 690, and 23%, respectively. Dexamethasone administered to nonacidotic adrenalectomized animals increased Pi ammonium and Ca2+ excretion 165, 240, and 31%, respectively. We conclude that changes in Pi, ammonium, and Ca2+ excretion observed during metabolic acidosis were dependent on intact adrenal glands and that glucocorticoids administered to adrenalectomized acidotic or nonacidotic animals mimicked the changes observed in acidotic animals with intact adrenal glands.
Na+-K+ pump stoichiometry and basolateral membrane permeability of frog corneal epithelium
Authors: Candia O. A. , Cook P.
Published: December 2017

The Na+-K+ pump flux ratio and the Na+ and K+ permeability of the basolateral membrane of the isolated frog corneal epithelium were studied with the aid of microelectrodes by analyzing the effects of ouabain, Ba2+, and amphotericin B. The experiments were done in Cl(-)-free solutions, a situation that approximates that of static head. Ouabain produced a quick depolarization of the potential difference across the basolateral membrane (PDb) from -72 to -62 mV without a change in resistance. Ba2+ (3 mM) rapidly lowered PDb from -74 to -57 mV and decreased the apical-to-basolateral resistance ratio. The effects of ouabain and Ba2+ were additive. The Na+-K+ flux ratio at the pump was calculated to be 1.78, substantially less than when the tissue is in a level flow condition, suggesting a variable stoichiometry. The K+ and Na+ resistances of the basolateral membrane were 15.7 and 5.5 k omega X cm2, respectively, allowing K+ and Na+ currents that approximately matched those produced by the Na+-K+ pump. The resistance of the basolateral membrane (4.0 k omega X cm2) was double that reported in Cl(-)-rich solutions, suggesting that Cl- contributes to the conductance of this membrane.
Increased PGE2 excretion by dDAVP in humans depends on state of hydration
Authors: Schwertschlag U. , Gerber J. G. , Barnes J. S. , Nies A. S.
Published: December 2017

The relationship of renal prostaglandin E2 (PGE2) excretion (UPGEV) to water deprivation, water diuresis, and subsequent antidiuresis by 1-desamino-8-D-arginine vasopressin (dDAVP) was studied in female volunteers. After 16 h of water deprivation, the subjects began a sustained water diuresis for 8 h. This diuresis caused a transient twofold rise in UPGEV at 2 h (P less than 0.05), which then fell back to or below baseline levels. dDAVP given during the water diuresis caused a transient rise of UPGEV as urine volume decreased and plasma osmolality fell from 277 +/- 1.5 to 271 +/- 2 mosmol/kg (P less than 0.01). Another group of subjects had the water diuresis discontinued after 4 h with dDAVP given at the 5th h when urine volume was decreasing and urine osmolality was increasing. In this setting dDAVP did not produce as great a fall in plasma osmolality nor did it increase UPGEV. These data indicate that renal prostaglandin synthesis (as determined by UPGEV) is increased transiently by an acute water load; dDAVP given during continued water ingestion results in a fall in plasma osmolality and increased PGE excretion; however, dDAVP does not increase UPGEV during normal hydration; and UPGEV is independent of changes in urine flow. These findings imply that renal prostaglandins may have a functional role in humans to inhibit the hydroosmotic actions of antidiuretic hormone, and thus hasten the excretion of a water load, and to prevent overhydration when inappropriate antidiuresis occurs. However, there is no evidence that the stimulus for prostaglandin production is dDAVP per se.
Effect of ADH on rubidium transport in isolated perfused rat cortical collecting tubules
Authors: Schafer J. A. , Troutman S. L.
Published: December 2017

Unidirectional fluxes of 86Rb+ were measured as an indicator of potassium transport in isolated rat cortical collecting tubules perfused and bathed at 38 degrees C with isotonic solutions in which Rb+ replaced K+. Under control conditions the lumen-to-bath flux (Jl----b) was significantly less than the bath-to-lumen flux (Jb----l), indicating net Rb+ secretion. Net secretion increased approximately 180% after addition of 100 microU/ml of arginine vasopressin (ADH) to the bathing solution, due to a rapid and reversible increase in Jb----l from 4.6 +/- 0.8 to 9.0 +/- 1.9 pmol X min-1 X mm-1 with no significant change in Jl----b. The ADH effect was completely inhibited by 2 mM luminal Ba2+. The average transepithelial voltage (Ve) was not significantly different from zero in the control period but became lumen negative (-5 to -10 mV) after ADH. With 10(-5) M amiloride in the lumen Ve was lumen positive (+2 to +4 mV) and was unaltered by ADH or Ba2+, yet ADH produced a significant but attentuated increase in Jb----l with no change in Jl----b. The results indicate that ADH augments net K+ secretion either by an increase in the Ba2+-sensitive conductance of the apical membrane or by an increase in the electrochemical potential driving force for net Rb+ secretion through this pathway.
Stimulation of chloride transport by HCO3-CO2 in rabbit cortical collecting tubule
Authors: Tago K. , Schuster V. L. , Stokes J. B.
Published: December 2017

We examined both the role of HCO3-CO2 in Cl transport as well as the effect of in vivo acid-base status on Cl transport by the rabbit cortical collecting tubule. The lumen-to-bath 36Cl tracer flux, expressed as the rate coefficient KCl, was measured in either HEPES-buffered (CO2-free) or HCO3-CO2-containing solutions. Amiloride was added to the perfusate to minimize the transepithelial voltage and thus the electrical driving force for Cl diffusion. Because KCl fell spontaneously with time in HCO3-CO2 solutions in the absence but not the presence of cAMP, we used cAMP throughout to avoid time-dependent changes. Acute in vitro removal of bath HCO3-CO2 reduced KCl. Acetazolamide addition in HEPES-buffered solutions also lowered KCl; KCl could be restored to control values by adding exogenous HCO3-CO2 in the presence of acetazolamide. In vivo acid-base effects on Cl transport were determined by dissecting tubules from either NaHCO3-loaded or NH4Cl-loaded rabbits. Tubules from HCO3-loaded rabbits had higher rates of Cl self exchange. Acute in vitro addition of bath HCO3-CO2 increased KCl and did so to a greater degree in tubules from HCO3-loaded rabbits. Most of this effect of HCO3-CO2 addition on KCl could not be accounted for by Cl-HCO3 exchange; rather, it appeared due to stimulation of Cl self exchange. The data are consistent with 36Cl transport occurring via Cl-HCO3 exchange as well as Cl self exchange. Both processes are acutely stimulated by HCO3 and/or Co2, and both are chronically regulated by in vivo acid-base status.
Abnormal renal hemodynamics and pressure-natriuresis relationship in Dahl salt-sensitive rats
Authors: Roman R. J.
Published: December 2017

The renal responses to changes in renal perfusion pressure (RPP) were compared in Dahl salt-resistant (R) rats and in prehypertensive and hypertensive Dahl salt-sensitive (S) rats to determine whether an abnormality in the pressure diuresis response is involved in the development of this form of hypertension. Possible differences in the neural and endocrine background to the kidney of S and R rats were eliminated by denervating the kidney and by holding plasma levels of vasopressin, aldosterone, corticosterone, and norepinephrine fixed by intravenous infusion. Arterial pressure averaged 124 +/- 1 mmHg in R rats, 133 +/- 1 mmHg in prehypertensive S rats, and 158 +/- 2 mmHg in hypertensive S rats. Control renal blood flows (RBF) and glomerular filtration rates (GFR) were not significantly different in the three groups. RBF was autoregulated over a range of pressures from 80 to 160 mmHg in normotensive S and R rats. GFR was autoregulated at pressures greater than 100 mmHg in R rats and greater than 120 mmHg in prehypertensive S rats. In contrast, RBF was only autoregulated at pressures greater than 110 mmHg in hypertensive Dahl S rats, and GFR was significantly reduced from control when RPP was lowered below 150 mmHg. In R rats, increasing RPP from 100 to 150 mmHg produced a fivefold increase in urine flow and sodium excretion. In prehypertensive or hypertensive Dahl S rats the slopes of the relationships between urine flow, sodium excretion, and RPP were less than half of those seen in R rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Body temperature: an important determinant of severity of ischemic renal injury
Authors: Zager R. A. , Altschuld R.
Published: December 2017

To assess the effects of body temperature on renal susceptibility to ischemic injury, rats were rendered acutely hypothermic (90-93 degrees F), normothermic (98-99 degrees F), or hyperthermic (101-103 degrees F) with a heat-controlled surgical board and then were subjected to 25 min of bilateral renal artery occlusion (RAO). Renal high-energy phosphates, their degradation products, and nonprotein sulfhydryl (NPSH) content were assessed at selected times during the peri-ischemic period. The severity of acute renal failure (ARF) was determined for 48 h following RAO by blood urea nitrogen (BUN) and plasma creatinine determinations and by renal histology. Ischemic ATP, ADP, AMP, GTP, GDP, UTP, and NAD levels and postischemic NPSH levels (15 min reflow) inversely correlated with temperature (P less than 0.001). BUN, creatinine concentrations (at 24 and 48 h), and histological injury (at 48 h) directly correlated with temperature (P less than 0.01). Hyperthermia in the absence of RAO had no demonstrable adverse renal effects. We conclude that hyperthermia potentiates ischemic renal injury, whereas hypothermia confers protection. These effects are associated with, and may be influenced by, temperature-induced changes in renal high-energy phosphate availability and oxidant stress during the ischemic/postischemic period.
Cellular organization of urinary acidification
Authors: Steinmetz P. R.
Published: December 2017

The turtle bladder contains transport systems for active sodium absorption, electrogenic proton secretion, and bicarbonate secretion (coupled to chloride absorption) that are functionally separate and occur in specialized epithelial cells. Maneuvers that alter the intracellular acid-base state, such as changes in PCO2, cause marked changes in the apical membrane area of alpha-type carbonic anhydrase (CA) cells by addition or retrieval of membrane vesicles but have no effect on the granular cells that transport sodium. The apical cell membrane of alpha-CA cells contains characteristic rod-shaped intramembrane particles (RSP) by freeze fracture and is coated on its cytoplasmic side with studs. A subpopulation of CA cells (beta-type), which is characterized by apical microvilli, fails to exhibit an apical response to CO2 stimulation and does not reveal RSPs or studs at its apical membranes; instead, these elements can be demonstrated at the basolateral membrane. The reversal in the polarity of these elements as well as physiological evidence suggest that beta-type cells are responsible for bicarbonate secretion. Structure-function studies of CO2 stimulation of H+ secretion by alpha-CA cells indicate that the secretion rate (JH) correlates with apical membrane area and numbers of RSPs. The view that RSPs represent arrays of transmembrane channels and that studs represent catalytic units of H+ pumps is supported by quantitative considerations but remains to be proven. Urinary acidification is regulated not only by changes in the number of H+ pumps but also by the intrinsic properties of the H+ pump itself. For a given pump population, JH is closely controlled by the delta microH across the active transport pathway.
Extrarenal potassium adaptation: role of skeletal muscle
Authors: Blachley J. D. , Crider B. P. , Johnson J. H.
Published: December 2017

Following the ingestion of a high-potassium-content diet for only a few days, the plasma potassium of rats rises only modestly in response to a previously lethal dose of potassium salts. This acquired tolerance, termed potassium adaptation, is principally the result of increased capacity to excrete potassium into the urine. However, a substantial portion of the acute potassium dose is not immediately excreted and is apparently translocated into cells. Previous studies have failed to show an increase in the content of potassium of a variety of tissues from such animals. Using 86Rb as a potassium analogue, we have shown that the skeletal muscle of potassium-adapted rats takes up significantly greater amounts of potassium in vivo in response to an acute challenge than does that of control animals. Furthermore, the same animals exhibit greater efflux of 86Rb following the termination of the acute infusion. We have also shown that the Na+-K+-ATPase activity and ouabain-binding capacity of skeletal muscle microsomes are increased by the process of potassium adaptation. We conclude that skeletal muscle is an important participant in potassium adaptation and acts to temporarily buffer acute increases in the extracellular concentration of potassium.
Immunodissection and culture of rabbit cortical collecting tubule cells
Authors: Spielman W. S. , Sonnenburg W. K. , Allen M. L. , Arend L. J. , Gerozissis K. , Smith W. L.
Published: December 2017

A mouse monoclonal antibody designated IgG3(rct-30) has been prepared that reacts specifically with an antigen on the surface of all cells comprising the cortical and medullary rabbit renal collecting tubule including the arcades. Plastic culture dishes coated with IgG3(rct-30) were used to isolate collecting tubule cells from collagenase dispersions of rabbit renal cortical cells by immunoadsorption. Typically, 10(6) rabbit cortical collecting tubule (RCCT) cells were obtained from 5 g of renal cortex (2 kidneys). Initial purity was greater than 96% based on immunocytofluorescent staining with three different anti-collecting tubule antibodies. Between 20 and 30% of the RCCT cells were reactive with peanut lectin suggesting that RCCT cells are a mixture of principal and intercalated cells. Approximately 10(7) RCCT cells were obtained after 4 to 5 days in primary culture. Moreover, RCCT cells continued to proliferate after passaging with a doubling time of approximately 32 h. RCCT cells passaged once and then cultured 4-5 days were found 1) to synthesize cAMP in response to arginine vasopressin (AVP), prostaglandin E2 (PGE2), isoproterenol, and parathyroid hormone, but not calcitonin, prostaglandin D2, or prostaglandin I, and 2) to release PGE2 in response to bradykinin but not arginine vasopressin or isoproterenol. Our results indicate that cultured RCCT cells retain many of the hormonal, histochemical, and morphological properties expected for a mixture of principal and intercalated rabbit cortical collecting tubule epithelia. RCCT cells should prove useful both for studying hormonal interactions in the cortical collecting tubule and as a starting population for isolating intercalated collecting tubule epithelia.
5-Methylnicotinamide inhibits renal brush-border phosphate transport with no change in NAD
Authors: Kempson S. A.
Published: December 2017

Administration of nicotinamide to rats produces a dose-dependent increase in nicotinamide adenine dinucleotide (NAD) content in the renal cortex and specific inhibition of sodium gradient-dependent phosphate transport across the renal brush-border membrane (BBM). Nicotinamide acts both as a precursor for NAD synthesis and as an inhibitor of NAD hydrolysis. To determine if the latter effect contributes to the change in phosphate transport, a nicotinamide analogue was used in the present study. 5-Methylnicotinamide (5MN) cannot support NAD synthesis, but it is an equipotent inhibitor of NAD-hydrolyzing enzymes. The characteristics of the specific inhibitory effect of nicotinamide on sodium gradient-dependent phosphate transport were reproduced by an equimolar dose (4 mmol/kg body wt) of 5MN. Unlike nicotinamide, the action of 5MN did not involve a change in renal cortical NAD content. These data indicate that inhibition of NAD hydrolyzing enzymes may be associated with inhibition of BBM phosphate transport, and this effect occurs independently of changes in NAD levels. These conclusions are supported by the finding that BBM phosphate transport was not inhibited by administration of nicotinic acid, an analogue that does not inhibit NAD hydrolysis.