bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of renal denervation on the suppression of renin secretion by vasopressin in conscious dogs
Authors: Gregory L. C. , Reid I. A.
Published: December 2017

Previous studies have shown that the inhibition of renin secretion by vasopressin (AVP) in conscious dogs is related to vasoconstrictor activity and may be a reflex response mediated by the renal nerves. The aim of the present experiments was to determine whether the suppression of plasma renin activity (PRA) by AVP is blocked by renal denervation. AVP and, for comparison, angiotensin II (ANG II) were infused intravenously for 45 min in seven conscious dogs before and after bilateral renal denervation. Before denervation, AVP infusion at 0.2 and 1.0 ng X kg-1 X min-1 suppressed PRA from 7.4 +/- 1.1 to 4.7 +/- 1.0 (P less than 0.01) and from 7.9 +/- 1.8 to 3.8 +/- 0.8 ng X ml-1 X 3 h-1 (P less than 0.01), respectively. ANG II infusion at 5.0 and 10.0 ng X kg-1 X min-1 decreased PRA from 7.5 +/- 2.3 to 2.5 +/- 0.7 (P less than 0.01) and from 6.0 +/- 1.1 to 1.8 +/- 0.4 ng X ml-1 X 3 h-1 (P less than 0.01), respectively. One to three weeks following renal denervation, PRA had decreased from 6.7 +/- 1.3 to 2.9 +/- 0.5 ng X ml-1 X 3 h-1 (P less than 0.01), and renal norepinephrine was undetectable. After denervation, neither AVP infusion at 0.2 (3.0 +/- 0.5 to 2.4 +/- 0.4 ng X ml-1 X 3 h-1) nor 1.0 ng X kg-1 X min-1 (3.1 +/- 0.8 to 2.8 +/- 1.0 ng X ml-1 X 3 h-1) suppressed PRA.(ABSTRACT TRUNCATED AT 250 WORDS)
Cl- transport via anion exchange in Necturus renal microvillus membranes
Authors: Seifter J. L. , Aronson P. S.
Published: December 2017

We investigated the mechanism of Cl- transport in microvillus membrane vesicles isolated from Necturus kidneys. Cl- influx was insensitive to changes in membrane potential induced by K+ gradients and the K+ ionophore valinomycin, arguing against conductive Cl- transport. Inward gradients of Na+ or Na+ + K+ did not stimulate initial Cl- influx, arguing against direct Na+-Cl- or Na+-K+-Cl- cotransport. External Cl-, HCO3-, and NO3- each stimulated 36Cl efflux and inhibited 36Cl uptake, indicating anion exchange. Outward HCO3- gradients but not OH- gradients stimulated 36Cl influx, consistent with Cl- -HCO3- exchange. Cl- transport via anion exchange was inhibited by furosemide, bumetanide, and disulfonic stilbenes, but not by acetazolamide. External halides stimulated 36Cl efflux (Cl- = Br- greater than I- greater than F-) but the organic anions lactate, p-aminohippurate, and urate did not. Amiloride-sensitive Na+-H+ exchange was demonstrated. Finally, in the presence of a CO2/HCO3 buffer system, imposing an inward Na+ gradient caused a time-delayed stimulation of 36Cl uptake, consistent with indirect coupling of Na+-H+ and Cl- -HCO3- exchangers. We conclude that the parallel operation of Na+-H+ and Cl- -HCO3- exchangers rather than direct cotransport may account for the Na+-coupled uphill Cl- entry previously observed in the intact proximal tubular cell of Necturus.
Intracellular acidosis blocks the basolateral Na-K pump in rabbit urinary bladder
Authors: Eaton D. C. , Hamilton K. L. , Johnson K. E.
Published: December 2017

The purpose of the experiments described in this paper was to examine the effect of intracellular pH on the basolateral Na+-K+-ATPase of rabbit urinary bladder cells. To modify the intracellular pH, we permeabilized the apical membrane of the bladder cells with the polyene antibiotic nystatin. To verify that the intracellular pH could be altered after nystatin treatment, the intracellular pH was monitored with pH-sensitive microelectrodes. (The normal intracellular pH was 7.1 +/- 0.11, n = 21.) After nystatin treatment, the intracellular pH over the range of pH 5.8 to 8.0 was indistinguishable from the mucosal pH. The cell-to-serosa, ouabain-inhibitable sodium flux showed a strong dependence on intracellular pH, with pH values more acidic or more alkaline than 7.4 producing substantial block. The magnitude of the alkaline block obeyed a sigmoidal relationship with a half block of Na+ flux near pH 8.1. The magnitude of the acidic block also obeyed a sigmoidal relationship with half block at pH 6.85. The combination of the two relationships produced a bell-shaped curve with a maximum between pH 7.3 and 7.6. The steepness of both relationships suggested that H+ ion was interacting with more than one site. At the normal intracellular pH (7.1), the Na pump was already partially blocked. This partial block, coupled with the steepness of the relationship between Na pump activity and intracellular H+ near pH 7.1, suggests that intracellular pH could be an important controlling factor for Na pump activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Passive potassium transport in the proximal convoluted tubule
Authors: Kaufman J. S. , Hamburger R. J.
Published: December 2017

Potassium transport in the isolated proximal convoluted tubule (PCT) of the rabbit was studied to determine the importance of concentration-dependent passive processes in potassium reabsorption. Net potassium flux was measured with an initial perfusate potassium concentration of 4 mM and bath potassium concentration of 2, 4, or 6 mM. When bath concentration was 6 mM, there was net potassium secretion in both superficial (SF) and juxtamedullary (JM) PCT. When bath concentration was 2 mM, there was net reabsorption in both groups of tubules. The apparent permeability coefficients were found to be significantly higher in JMPCT (2.96 +/- 0.37 pmol X mm-1 X min-1 X mM-1) than in SFPCT (1.94 +/- 0.34 pmol X mm-1 X min-1 X mM-1). We also attempted to uncover an active potassium reabsorption process by inhibiting water flux, but not other transport processes, by the imposition of a transtubular osmotic gradient. When the perfusate was made 30 mosmol/kg H2O hypertonic to the bath, there was net fluid entry of 0.38 +/- 0.09 nl/min, accompanied by a significant decline in net potassium flux. The collected fluid-to-perfusate potassium concentration ratio was not significantly less than zero, thereby not providing evidence for active potassium reabsorption. These studies suggest that a primary mode of potassium reabsorption in this segment is due to its movement along a transepithelial gradient established by fluid reabsorption. We have been unable to identify an active component of potassium reabsorption.
1,25(OH)2D3 binding along the rat nephron: autoradiographic study in isolated tubular segments
Authors: Manillier C. , Farman N. , Bonjour J. P. , Bonvalet J. P.
Published: December 2017

1,25-dihydroxyvitamin D3 [1,25(OH)2D3] binding sites were studied along the nephron of rats. The animals were pretreated with the diphosphonate EHDP at doses that inhibit the endogenous production of 1,25(OH)2D3. A dry film autoradiographic technique was applied to tubular segments isolated by microdissection from kidneys incubated in vitro with various concentrations (0.2-12 nM) of [3H]1,25(OH)2D3 in the presence or absence of an excess unlabeled hormone (X200) in order to determine specific binding. Total, nonspecific, and specific labeling were quantified by silver grain counting over cytoplasmic and nuclear areas. Specific nuclear labeling appeared in the cortical ascending limb and papillary collecting tubule at 1 nM. In the distal tubule and, to a lesser extent, in the cortical collecting tubule a specific nuclear labeling was also present, but only at higher concentrations. No specific nuclear labeling was detected in the proximal tubule. All along the nephron, a significant and nonspecific labeling was observed in the cytoplasm, either alone or superimposed over the specific nuclear labeling. In conclusion 1,25(OH)2D3 specific binding sites appear to be localized mainly in the cortical ascending limb of the loop of Henle, in the distal and cortical collecting duct, and in the papillary collecting duct.
Protective effect of thyroxine but not parathyroidectomy on gentamicin nephrotoxicity
Authors: Cronin R. E. , Newman J. A.
Published: December 2017

Gentamicin nephrotoxicity increases renal cortex calcium and sodium and decreases renal cortex Na-K-ATPase activity. Human acute renal failure is accompanied by an increase in parathyroid hormone (PTH), a hormone that stimulates calcium uptake by tissues, and by a decrease in thyroid hormone, a hormone that increases renal cortex Na-K-ATPase activity. This study evaluated the role of extracellular calcium, PTH, and thyroxine in the pathogenesis of gentamicin nephrotoxicity. Chronically parathyroidectomized hypocalcemic rats (PTXG) given gentamicin (30 mg/kg s.c. twice daily for 8 days) were not protected from renal failure when compared with intact rats given gentamicin (NG), serum creatinine being 4.4 +/- 1.0 and 3.7 +/- 0.7 mg/dl, respectively, compared with normals (N), 1.2 +/- 0.1 mg/dl. Rats given thyroxine (10 micrograms/100 g body wt for 10 days) before and during gentamicin (PTXT4G) had a serum creatinine not significantly different from normals, 2.1 +/- 0.4 mg/dl. Plasma T4 was reduced in PTXG, NG, and PTXT4G compared with N, but the value for PTXT4G was significantly higher than for either PTXG or NG. Renal cortex Na-K-ATPase activity (mumol Pi X mg prot-1 X h-1) was lower in PTXG (2.3 +/- 0.2) and NG (2.4 +/- 0.5) compared with N (3.7 +/- 0.1), but activity was not reduced in PTXT4G (3.2 +/- 0.2) Thyroxine was protective also against gentamicin nephrotoxicity in intact rats. Clearance and excretion studies indicated that this protection did not result from an increase in glomerular filtration rate, filtered load of calcium, or urinary calcium excretion.(ABSTRACT TRUNCATED AT 250 WORDS)
Evidence that aldosterone influences transport in target tissues by dissimilar mechanisms
Authors: Hirsch D. , Pace P. , Binder H. J. , Hayslett J. P.
Published: December 2017

The present study was performed to answer the question: Is the action of aldosterone on electrolyte transport and electrical properties similar in all target tissues? Studies were performed in vivo in control animals and rats with secondary hyperaldosteronism, caused by a sodium-free diet, to compare the effects of hyperaldosteronism on distal colon with hormone-induced changes in proximal colon. In distal colon aldosterone increased net sodium absorption and potassium secretion approximately threefold. Transmural potential difference increased from -15 +/- 2 to -83 +/- 3 mV (lumen negative) and ISC rose from 167 +/- 26 to 1,023 +/- 17 microA X cm-2. These aldosterone-induced responses were completely inhibited by 0.1 mM amiloride. In contrast, in proximal colon potential difference was unchanged or increased slightly in experimental animals and ISC increased only 28% above control, although increases in net sodium and potassium transport were similar to changes observed in distal colon. Amiloride did not reduce sodium absorption in proximal colon of animals with hyperaldosteronism; ISC was decreased by 43%. These studies demonstrate that rat proximal colon is an aldosterone-sensitive tissue, but that the mechanism by which aldosterone influences sodium transport is not identical in distal and proximal portions of colon.
Viewing the kidney through microelectrodes
Authors: Frömter Eberhard
Published: December 2017

Page F695: A footnote acknowledged presentation of the Homer Smith Award Lecture by Dr. Eberhard Frömter to be supported by the New York Heart Association. However, since 1983, the Homer Smith Award Lecture has been jointly sponsored by the New York Heart Association and the American Society of Nephrology.
Dietary protein intake conditions the degree of renal vasoconstriction in acute renal failure caused by ureteral obstruction
Authors: Ichikawa I. , Purkerson M. L. , Yates J. , Klahr S.
Published: December 2017

Whole kidney inulin (CIn) and PAH (CPAH) clearances were measured after unilateral release of bilateral ureteral obstruction (BUO) of 24-h duration in rats fed for 4 wk isocaloric diets containing either 40% casein (high protein diet) or 6% casein (low protein diet). Values for CIn and CPAH were markedly depressed in both groups but to a greater extent in high protein-fed rats, averaging less than 60% of values measured in low protein-fed animals. Captopril, an inhibitor of the angiotensin I converting enzyme, increased CIn and CPAH markedly but comparably in high or low protein fed rats. Micropuncture studies performed after unilateral release of BUO in another group of rats fed a high or a low protein diet revealed lower levels of glomerular plasma flow rate (QA) and single nephron glomerular filtration rate (SNGFR) in rats fed a high protein diet. Values for renal arteriolar resistances were nearly twofold in high as compared with low protein-fed animals. Infusion of OKY-1581, an inhibitor of thromboxane A2 synthetase, increased both QA and SNGFR, decreased arteriolar resistances, and increased glomerular capillary ultrafiltration coefficient in high but not in low protein-fed rats. Urinary thromboxane B2 excretion per milliliter of GFR was greater in rats fed a high protein diet than in those fed a low protein diet after release of BUO but not in normal rats. In normal rats infusion of OKY-1581 did not increase CIn or CPAH.(ABSTRACT TRUNCATED AT 250 WORDS)
Cyanate and temperature regulation in anephric rabbits
Authors: Eiger S. M. , Kluger M. J.
Published: December 2017

Knochel and Seldin proposed that the lowered body temperature observed during uremia was caused by an elevation in the circulating levels of cyanate. To test this hypothesis, normal rabbits were infused with varying concentrations of sodium cyanate. Infusion of pharmacological doses of cyanate (plasma concentration rose to 1,080 +/- 70 microM, n = 5) resulted in reductions in body temperature similar to that found during uremia; however, when normal rabbits were nephrectomized the plasma cyanate concentration only rose from 3.7 +/- 1.6 to 18 +/- 1.8 microM (n = 8) by 1-day postnephrectomy (body temperature fell 0.33 +/- 0.1 degrees C, n = 6). Plasma cyanate concentration did not rise further on days 2 and 3 postnephrectomy, despite a continued fall in body temperature. Infusion of cyanate in control rabbits to plasma concentrations attained 1-3 days postnephrectomy did not result in a fall in body temperature. Based on the failure of pathophysiological concentrations of cyanate to cause a reduction in the body temperature of normal rabbits, we conclude that cyanate is not responsible for the lowered body temperature associated with the acute response to uremia.
Phosphate uptake by proximal cells isolated from rabbit kidney: role of dexamethasone
Authors: Poujeol P. , Vandewalle A.
Published: December 2017

A single cell suspension was prepared from rabbit kidney cortex by gentle mechanical dissociation. The isolated cells were functionally intact and metabolically active, as indicated by exclusion of eosin dye, respiratory measurement, and ATP content. The isolated cells were shown to possess long microvilli, and their proximal origin was confirmed by enzymatic and glucose production studies. The uptakes of 0.1 mM phosphate (Pi) and 0.05 mM D-glucose at 37 degrees C were strongly dependent on the extracellular Na+. Incubation of the cells with parathyroid hormone (10 U/ml) for 20 min reduced 20-s Pi uptake by 20%. The addition of dibutyryl cAMP decreased Pi uptake, with a maximal effect at 10(-6) M. Incubation of cells with gluconeogenic substrates, under conditions in which glucose production was increased, did not promote any change in Pi accumulation. When incubated for 60 min at 37 degrees C in the presence of dexamethasone (Dex), the Na+-dependent Pi uptake was decreased by 29% at 10(-9) M and by 36% at 10(-7) M without modification of the glucose uptake. Replacing Dex by aldosterone (10(-7) M) remained without effect on Pi uptake. It is concluded that: renal cells isolated by our preparative method are mainly of proximal origin; isolated cells are a good model for studying the regulation of Pi uptake in the proximal tubule; and glucocorticoids have an acute specific effect on Pi transport detectable in vitro and this effect does not seem to be related to modifications of renal gluconeogenesis.
Effect of calcium on transport characteristics of cultured proximal renal cells
Authors: Sakhrani L. M. , Tessitore N. , Massry S. G.
Published: December 2017

We examined the effects of acute changes in extracellular and intracellular calcium on transport processes in primary culture of proximal rabbit renal cells. A change in extracellular calcium from 0 to 3 mM inhibited amiloride-sensitive sodium uptake by 30%, and this effect was maximal at 1 mM calcium. Other polyvalent cations (Mn2+, Mg2+, La3+, and Ba2+) produced quantitatively similar inhibition of amiloride-sensitive sodium uptake compared with calcium. An increase in cytosolic calcium produced by calcium loading (20 mM) or by A23187 (20 microM) resulted in an inhibition of 25-40% of amiloride-sensitive sodium uptake. Moreover, quinidine (10(-4)M) and ruthenium red (3 microM), agents presumed to increase cytosolic calcium, inhibited amiloride-sensitive sodium uptake by 20-60%. Both these agents also inhibited sodium-dependent phosphate uptake by 20% but had no effect on ouabain-sensitive 86Rb+ uptake or on sodium-dependent alpha-methylglucoside uptake. Our data indicate that increases in extracellular calcium inhibit amiloride-sensitive sodium uptake and increases in cytosolic calcium inhibit sodium-dependent phosphate and amiloride-sensitive sodium uptakes. The effect of extracellular calcium may be due to charge screening and/or binding to the negatively charged plasma membrane or due to alterations in membrane fluidity.
Bicarbonate transport by isolated perfused rat collecting ducts
Authors: Atkins J. L. , Burg M. B.
Published: December 2017

Previously, bicarbonate transport was measured in isolated perfused rabbit cortical collecting ducts (CCD) and outer medullary collecting ducts (OMCD). Rabbit CCD either absorbed or secreted bicarbonate in vitro, depending on whether the animals were treated with NH4Cl or NaHCO3, but the OMCD absorbed bicarbonate regardless of the treatment. The general significance of these findings (particularly the bicarbonate secretion) was questioned because rabbits are herbivores that normally excrete alkaline urine. Therefore, we have now studied rats, an omnivorous species, that normally excrete acid urine. The overall pattern of bicarbonate transport in rats was similar to that previously found in rabbits. CCD from rats given NaHCO3 initially secreted bicarbonate, but those from rats given NH4Cl absorbed bicarbonate. Rat OMCD all absorbed bicarbonate, regardless of the treatment. The significant differences between the results with rats and rabbits were 1) a marked shift in bicarbonate transport in control and bicarbonate-loaded rat (but not rabbit) CCD with time of perfusion in vitro from secretion toward absorption; this implies an additional regulatory mechanism in rats; and 2) rat OMCDs absorbing bicarbonate more than three times faster than rabbit OMCD. These results provide additional evidence that conditioned changes in cortical collecting duct bicarbonate transport, now observed in two different species, play a significant role in the control of net acid excretion.
A double-membrane model for urinary bicarbonate secretion
Authors: Stetson D. L. , Beauwens R. , Palmisano J. , Mitchell P. P. , Steinmetz P. R.
Published: December 2017

To define the transport pathway for HCO-3 secretion (JHCO3) across the apical and basolateral membranes of turtle bladder, we examined the effects of cAMP, isobutylmethylxanthine (IBMX), the Cl- channel blocker 9-anthroic acid (9-AA), and the disulfonic stilbene DIDS (4,4'-diisothiocyanostilbene-2,2'-sulfonic acid) on the electroneutral and electrogenic components of JHCO3. Total JHCO3 was measured by pH stat titration of the mucosal compartment after Na+ absorption and H+ secretion were abolished by ouabain and a delta pH, respectively. Addition of cAMP or IBMX increased total JHCO3 and induced a short-circuit current (ISC), accounting for a large part of JHCO3; net Cl- absorption was reduced. Mucosal 9-AA inhibited the IBMX-induced electrogenic component of JHCO3, whereas mucosal DIDS inhibited the electroneutral component and acetazolamide reduced both. We suggest that HCO-3 is generated within the cell by a Na-independent primary active acid-base transport at the basolateral membrane (H+ extrusion into the serosal compartment). Cellular HCO-3 accumulation drives JHCO3 via a Cl-HCO3 exchanger at the luminal membrane. IBMX and cAMP activate a 9-AA-sensitive anion conductance parallel to the exchanger. The apparent reversal of the transport elements between the two cell membranes (compared with H+-secreting cells) led to an ultrastructural examination of the carbonic anhydrase-rich cells.
cAMP- and beta-adrenergic-stimulated chloride-dependent Ca2+ secretion in frog skin
Authors: Ziyadeh F. N. , Kelepouris E. , Civan M. M. , Agus Z. S.
Published: December 2017

This study examined the possible existence and nature of Ca2+ transport in frog skin using 45Ca fluxes and short-circuiting technique. Following the addition to full-thickness frog skin (FTFS) of 8-[p-chlorophenylthio]cAMP (8-CPT-cAMP), forskolin, or 1-methyl-3-isobutylxanthine, the secretory Ca2+ flux increased severalfold, inducing net Ca2+ secretion. The absorptive flux was unchanged. Isoproterenol (10(-6)M) reproduced the effects of cAMP on Ca2+ secretion (-3.76 +/- 0.80 nmol X cm-2 X h-1 vs. +0.04 +/- 0.05 in control) while vasopressin and parathyroid hormone did not alter Ca2+ fluxes. Because FTFS contains subepidermal glands capable of Cl- secretion in response to beta-adrenergic stimulation, split-thickness frog skin (STFS) consisting of the gland-free Na-absorbing surface epithelium was used to localize the anatomic site of Ca2+ secretion. In STFS, addition of 8-CPT-cAMP or isoproterenol failed to induce Ca2+ secretion, suggesting that this transport in FTFS is localized in skin glands. Additional studies explored the relationship between Ca2+ and Cl- transport in FTFS. Furosemide prevented the stimulation of both Ca2+ and Cl- secretion. Removal of Cl- from the bathing medium abolished Ca2+ secretion. Thus, FTFS exhibits a beta-adrenergic, cAMP-stimulated net Ca2+ secretion that is Cl- dependent. As this effect is not observed in STFS, the pathway of Ca2+ secretion in frog skin is probably localized in the subepidermal glandular epithelium in association with Cl- secretion. Frog skin glands may represent a useful model for the study of Ca2+ transport in Cl--transporting epithelia.
Glomerular permselectivity in the isolated perfused rat kidney
Authors: Boyce N. W. , Holdsworth S. R.
Published: December 2017

Glomerular permselectivity characteristics were studied in the Sprague-Dawley rat in vivo and in the isolated rat kidney perfused with an erythrocyte-free Krebs-Henseleit buffered 5% albumin solution (IPK). IPK permselectivity in vitro, assessed by fractional clearances of neutral dextran (FCND) and dextran sulfate (FCDS) with molecular radii 18-43 A, was essentially similar to that of the Sprague-Dawley rat in vivo. The negative charge barrier of the IPK glomerular filter was intact [e.g., FCND of 36 A = 0.10 +/- 0.01 (SE) vs. FCDS of 36 A = 0.01 +/- 0.00 (P less than 0.01)]. Dextrans of an intermediate size (26-34 A) had lower fractional clearances in the IPK than in vivo [e.g., FCND of 30 A in IPK = 0.23 +/- .04 vs. FCND of 30 A in vivo 0.40 +/- 0.01 (P less than 0.01)]. This decreased clearance of dextrans of an intermediate molecular size is predicted by pore theory, since the IPK has an increased afferent glomerular plasma flow rate. As glomerular permselectivity characteristics in the IPK simulate in vivo characteristics, such preparations are suitable in vitro models in which to study factors that modulate permselectivity. The demonstration that the glomerular filter in the IPK has a normal negative charge barrier indicates that the increased protein excretion in IPK systems cannot be attributed to abnormalities of this component of the filtration barrier.
Role of renal nerves in maintaining sodium balance in unrestrained conscious rats
Authors: Fernandez-Repollet E. , Silva-Netto C. R. , Colindres R. E. , Gottschalk C. W.
Published: December 2017

This study was designed to investigate the effects of bilateral renal denervation on sodium and water balance, the renin-angiotensin system, and systemic blood pressure in unrestrained conscious rats maintained on a normal- or low-sodium diet. Renal denervation was proven by chemical and functional tests. Both bilaterally denervated rats (n = 18) and sham-denervated rats (n = 15) maintained positive sodium balance while on a normal sodium intake. Both groups were in negative sodium balance for 1 day after dietary sodium restriction was instituted but were in positive sodium balance for the following 9 days. Systolic blood pressure was higher in sham-denervated (115 +/- 3 mmHg) than in denervated rats (102 +/- 3 mmHg) while on a normal diet (P less than 0.05) and remained so during sodium restriction. Plasma renin concentration (PRC) and plasma aldosterone concentration (PAC) were significantly diminished in the denervated rats during normal sodium intake (P less than 0.05). After dietary sodium restriction, PRC increased in both groups but remained significantly lower in the denervated rats (P less than 0.05). Following dietary sodium restriction, PAC also increased significantly to levels that were similar in both groups of rats. These results demonstrate that awake unrestrained growing rats can maintain positive sodium balance on a low sodium intake even in the absence of the renal nerves. However, efferent renal nerve activity influenced plasma renin activity in these animals.
Actions of NAD+ on renal brush border transport of phosphate in vivo and in vitro
Authors: Kempson S. A. , Turner S. T. , Yusufi A. N. , Dousa T. P.
Published: December 2017

Previous studies showed that an increase in NAD+ content in renal cortex in vivo was accompanied by specific inhibition of Na+-dependent inorganic phosphate (Pi) transport across the renal brush border membrane (BBM). Further, in vitro addition of NAD+ to isolated renal BBM vesicles specifically inhibited Na+ gradient-dependent transport of Pi. The present study examined some aspects of the mechanism of this inhibition by NAD+ in vitro and in vivo. When NAD+ was increased in vivo by nicotinamide injection, the apparent Vmax was decreased, but the apparent Km was not different, indicating apparent noncompetitive inhibition. In the presence of 0.3 mM NAD+ added in vitro, the apparent Km for Na+-dependent Pi transport by BBM vesicles was increased, whereas the apparent Vmax was unchanged, indicating apparent competitive inhibition. These changes in apparent Km and apparent Vmax were identical when Pi uptake was measured either at 30-s or at 5-s (the initial rate) incubation times. Inhibition of Pi transport by BBM vesicles in vitro was due primarily to the action of intact added NAD+, although there may be some contribution by isotope dilution due to Pi released from NAD+ by enzymatic hydrolysis. Although in vitro inhibition of Pi transport by added NAD+ was reversed by washing the BBM, the inhibition due to increased NAD+ in vivo persisted after extensive washing of the isolated BBM. The specificity of the inhibitory effect of NAD+ in vivo was indicated by the finding that changes in renal cortical content of ATP or Pi, evoked by loading with glycerol or fructose, did not change BBM transport of Pi.(ABSTRACT TRUNCATED AT 250 WORDS)
Dynamics of nucleotides in distal nephron of mice with nephrogenic diabetes insipidus
Authors: Kusano E. , Yusufi A. N. , Murayama N. , Braun-Werness J. , Dousa T. P.
Published: December 2017

In mice with hereditary nephrogenic diabetes insipidus (NDI), the high activity of cAMP-phosphodiesterase (cAMP-PDIE) in medullary collecting tubules (MCT) prevents the increase in cAMP content in response to vasopressin [Arg8]vasopressin (AVP). Even when the cAMP response to AVP is partly corrected by cAMP-PDIE inhibitor 1-methyl-3-isobutylxanthine (MIX), under all tested conditions the cAMP levels in MCT of NDI mice remained much lower than in controls (B. A. Jackson, R. M. Edwards, H. Valtin, and T. P. Dousa, J. Clin. Invest. 66: 110-122, 1980). In the present study, we explored which factors may account for this defect. We determined contents of ATP, nicotinamide adenine dinucleotide (NAD), and the levels of cAMP in MCT and in medullary thick ascending limb of Henle's loop (MAL) microdissected from control and NDI mice. In the presence of 1 microM AVP and 0.05 mM MIX, the cAMP levels accumulated in MCT of NDI mice were four times lower compared with controls, but the levels of ATP and NAD were not different. ATP levels in MAL of NDI mice were slightly (delta -23%) lower than in MAL from controls, and in distal convoluted tubules (DCT) of NDI mice the ATP levels were also decreased (delta -49%). Although AVP alone had little effect on cAMP levels in mouse MAL in the presence of 0.1 mM forskolin, the AVP elicited a 20-fold increase of cAMP of both the control and NDI mice. Addition of 0.1 mM forskolin further increased the cAMP accumulation in MCT incubated with AVP.(ABSTRACT TRUNCATED AT 250 WORDS)
Renal hemodynamics and arterial pressure during chronic intrarenal adenosine infusion in conscious dogs
Authors: Hall J. E. , Granger J. P.
Published: December 2017

The major aim of this study was to examine the chronic effects of increased intrarenal adenosine (ADO) levels on control of renal hemodynamics and mean arterial pressure (MAP). In six uninephrectomized conscious dogs, intrarenal ADO infusion (2 micrograms . kg-1 . min-1) for 6 days caused no significant changes in MAP, which averaged 94 +/- 3 mmHg during the control period and 91 +/- 2 mmHg during ADO infusion. ADO infusion for 6 days decreased glomerular filtration rate (GFR) and filtration fraction while causing no significant changes in effective renal plasma flow (ERPF) or sodium and water balance. To examine the role of angiotensin II (ANG II) in altering the blood pressure and renal effects of ADO, we also studied the effects of intrarenal ADO infusion in five uninephrectomized conscious dogs during continuous intrarenal infusion of ANG II (1 ng . kg-1 . min-1) to prevent renal levels of ANG II from decreasing. However, even when renal ANG II levels were maintained constant, ADO infusion at 2 micrograms . kg-1 . min-1 for 4 days and 10 micrograms . kg-1 . min-1 for 5 days failed to alter MAP, which averaged 104 +/- 6 mmHg during the control period, 106 +/- 5 mmHg during infusion of 2 micrograms . kg-1 . min-1, and 105 +/- 5 mmHg during infusion of 10 micrograms. . kg-1 . min-1 ADO. Intrarenal ANG II infusion did not prevent decreases in GFR and filtration fraction during ADO infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of blood viscosity on plasma renin activity and renal hemodynamics
Authors: Simchon S. , Chen R. Y. , Carlin R. D. , Fan F. C. , Jan K. M. , Chien S.
Published: December 2017

The effects of alterations in apparent blood viscosity on renal hemodynamics and plasma renin activity (PRA) were studied in dogs anesthetized with sodium pentobarbital. Blood viscosity was altered isovolemically either by changes in hematocrit (Hct) or by an increase in plasma viscosity (dextran administration). Arterial blood pressure and renal blood flow (RBF) remained relatively constant when apparent blood viscosity was elevated by changes in Hct or plasma viscosity. Thus the hyperviscosity of blood was associated with a decrease of renal vascular hindrance, resulting in an essentially unchanged renal flow resistance. The decrease in renal vascular hindrance may result from renal vasodilation. In hyperviscosity induced with dextran, the increase in PRA correlates linearly with the decrease in renal vascular hindrance, with a coefficient of correlation of 0.968 (P less than 0.005). The increase in PRA that resulted when Hct was raised from 25 to 55% also can be correlated linearly with the decrease in renal vascular hindrance, with a coefficient of correlation of 0.953 (P less than 0.005). These results suggest that the decrease in renal vascular hindrance in response to a rise in apparent blood viscosity leads to an increase in PRA.
pH sensitivity of the basolateral membrane of the rabbit proximal tubule
Authors: Biagi B. A. , Sohtell M.
Published: December 2017

Conventional microelectrodes were used to study the effects of bath pH and bicarbonate concentrations on the basolateral membrane potential (Vbl) of cells from the superficial proximal convoluted (PCT) and proximal straight (PST) tubules of the rabbit kidney perfused in vitro. Bathing solution pH was varied over the range of 5.9-7.4 using either control (22-25 mM) or low bicarbonate (5.0-6.6 mM) Ringer solutions and the appropriate CO2 tensions. The results show a strong pH dependence of the steady-state values of Vbl in both the convoluted and straight tubule segments. The pH-dependent depolarization was approximately 35 mV/pH unit change of the bathing solution in the acid direction and could be demonstrated in CO2-free HEPES-buffered solutions. A depolarizing response to increased bath potassium concentration (HK) was observed that was linearly related to the absolute value of the Vbl under control conditions. Under acidotic conditions, reduced HK depolarizations indicate that a decrease in the relative potassium permeability of the basolateral membrane is the principle mechanism underlying the effects of bath pH on Vbl.
Electrophysiology of basolateral bicarbonate transport in the rabbit proximal tubule
Authors: Biagi B. A. , Sohtell M.
Published: December 2017

Conventional microelectrodes were used to examine the electrogenic pathways for bicarbonate transport across the basolateral membranes of proximal convoluted (PCT) and straight (PST) tubule segments of the rabbit kidney perfused in vitro. When bath bicarbonate concentration was reduced from 22 to 6.6 mM at a constant pH, transient depolarizations lasting several seconds with a peak value of approximately 15 mV were seen in both tubule segments. Acetazolamide (0.1 mM) in the lumen and bath solutions reduced the magnitude and increased the duration fo this response. The final pH of the bathing solution influenced both the peak height and steady-state values of the intracellular potential when bicarbonate concentration was reduced either with constant CO2 or with an increase in CO2. Reducing bath sodium concentration by replacement with either tetramethylammonium or N-methyl-D-glucamine resulted in a sustained depolarization of both PCT and PST cells. This response was inhibited by the addition of 10(-4) M 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS) in the bathing solution. By analogy with bicarbonate transport in rat and amphibian proximal tubules, these data suggest that bicarbonate exit across the basolateral membrane of the rabbit proximal tubule is electrogenic and coupled to sodium and that basolateral bicarbonate exit can be inhibited by both acetazolamide and SITS in the bathing solution.
Dissociation of CO2 hydration and renal acid secretion in the dogfish, Squalus acanthias
Authors: Swenson E. R. , Maren T. H.
Published: December 2017

Maximal rates of renal hydrogen ion secretion and bicarbonate reabsorption in the dogfish were stimulated by intravascular infusion of acidic and basic buffers: bicarbonate, phosphate, phenol red, dimethadione (DMO), imidazole, and piperazine-N,N'-bis(2 ethanesulfonic acid) (PIPES). There was no difference in titratable acid secretion or urinary pH after bicarbonate infusion despite a sevenfold increase in plasma bicarbonate. Bicarbonate reabsorption was increased 12-fold and showed no evidence of reaching a maximum. This was not altered by methazolamide, as expected, since there is no renal carbonic anhydrase in seagoing fish. Imidazole resulted in the greatest augmentation of renal titratable acid secretion (33----390 mueq . h-1 . kg-1) and did not alter urinary pH. Inhibition of organic base secretion by Darstine had no effect on the imidazole-induced maximal rate of acid secretion. This rate was compared with that of hydrogen ion generation calculated from the uncatalyzed reactions of CO2 and H2O or OH-, maximizing PCO2 and OH- gradients and reaction volumes in vivo. These calculated chemical rates could only account for 9-14% of the measured maximal acidification rate. Thus the powerful process that maintains constant acid urine pH is not only independent of carbonic anhydrase but can function well in a low CO2 environment in which the reactions CO2 + H2O or CO2 + OH- do not furnish enough protons for H+ secretion or HCO3- reabsorption. We conclude that following the cellular protolysis of water, processes other than those involving CO2 buffering of OH- permit H+ to engage in the formation of urine.
Characteristics of the Na+-H+ antiporter in the intact renal proximal tubular cell
Authors: Nord E. P. , Goldfarb D. , Mikhail N. , Moradeshagi P. , Hafezi A. , Vaystub S. , Cragoe E. J. , Fine L. G.
Published: December 2017

The characteristics of the proximal tubular Na+-H+ antiporter were determined in isolated proximal tubular cells to ascertain whether the features of this transport system in intact cells are comparable with those previously described for isolated brush-border membrane vesicles. A method is described for the rapid isolation of a purified preparation of cells that demonstrate morphological and functional characteristics of the renal proximal tubule. The cells maintain their polarity while in suspension, and adenylate cyclase activity is enhanced by parathyroid hormone but not by arginine vasopressin. The cells display gluconeogenic function and Na+-dependent alpha-methyl-D-glucose and organic phosphate cotransport, processes that confirm their proximal tubule origin. O2 consumption rates and cytosolic adenosine triphosphate levels indicate functional integrity. Na+-H+ antiport activity was defined in these cells by measuring amiloride-sensitive Na+ uptake. At intracellular pH = 6.4 vs. extracellular pH = 7.4, KtNa was 10.1 +/- 2.8 mM, and maximal sodium flux was 0.89 +/- 0.13 nmol X 10(6) cells-1 X K0.5 for amiloride and ethyl-isopropyl amiloride, measured at an external Na+ concentration of 1 mM, was observed at 2.5 X 10(-5) M and 2.9 X 10(-6) M, respectively. The external and internal loci of the exchanger displayed asymmetric affinity for the hydrogen ion: the apparent pK for the external site was 7.20-7.26 vs. less than 6.5 for the internal site. The internal site demonstrated features of positive cooperativity. In summary, the Na+-H+ antiporter present in the luminal membrane of the renal proximal tubule has been characterized in the intact cell and displays functional and kinetic parameters closely resembling those described in isolated brush-border membrane vesicles.
Evidence for electroneutral sodium chloride transport in rat proximal convoluted tubule
Authors: Howlin K. J. , Alpern R. J. , Berry C. A. , Rector F. C.
Published: December 2017

One- to two-thirds of NaCl absorption in the late proximal convoluted tubule (no luminal organic solutes present) is inhibited by cyanide and thus is dependent on active transport. To examine whether this active transport-dependent NaCl transport is electrogenic or electroneutral, the effect of cyanide on transepithelial potential difference (PD) was measured in the rat proximal convoluted tubule microperfused in vivo. In the presence of an ultrafiltrate-like luminal perfusate containing glucose and alanine, cyanide addition caused the transepithelial PD to change from -0.44 +/- 0.04 to -0.05 +/- 0.03 mV (P less than 0.001). In the presence of a late proximal tubular fluid (high chloride, low bicarbonate, no organics), the transepithelial PD was 1.23 +/- 0.06 mV and was unchanged at 1.19 +/- 0.05 mV after cyanide addition (NS). To eliminate the possibility that an effect of cyanide on a putative acidification-dependent lumen-positive PD was concealing an effect on an electrogenic sodium transport-dependent lumen-negative PD, the above studies were repeated in the presence of acetazolamide. Cyanide did not affect the transepithelial PD (1.17 +/- 0.05 vs. 1.07 +/- 0.06 mV, NS). We conclude that, although cyanide-inhibitable NaCl transport is electrogenic in the presence of luminal organic solutes, it does not generate a transepithelial PD in their absence and therefore is electroneutral.
A servo-system for constant pressure perfusion of the isolated rat kidney
Authors: Scaduto R. C. , Schoolwerth A. C.
Published: December 2017

A technical difficulty in perfusion of the isolated rat kidney has been the regulation of perfusion pressure. Since perfusion pressure is an important determinant of renal function, this parameter should be well regulated for experimental consistency. A servo-system is described that uses analog circuitry to calculate and maintain the cannula tip pressure for perfusion of the isolated kidney. The system is sufficiently responsive to maintain a constant perfusion pressure during the rapid changes in renal resistance caused by addition of angiotensin II or epinephrine to the perfusate. Analog outputs are provided for the recording of perfusion flow rate, perfusion pressure, and renal resistance.
Effect of albumin on glomerular ultrafiltration coefficient in isolated perfused dog glomerulus
Authors: Fried T. A. , McCoy R. N. , Osgood R. W. , Stein J. H.
Published: December 2017

To evaluate the direct effect of albumin concentration on the glomerular capillary ultrafiltration coefficient (Kf), we compared the effect of "normal" (3.4 g/100 ml), "low" (0.1 g/100 ml), and "no albumin" (less than 0.005 g/100 ml) concentration on the determinants of single-nephron glomerular filtration rate (SNGFR) as measured with the isolated perfused glomerulus technique. When the albumin concentration was decreased from normal to low concentrations, the afferent flow rate increased from 318 +/- 147 (mean +/- SE) to 450 +/- 174 nl/min, the filtration fraction increased from 0.19 +/- 0.04 to 0.35 +/- 0.08, and the SNGFR increased from 49 +/- 21 to 126 +/- 34 nl/min. These changes were associated with a small though significant increase in Kf from 2.79 +/- 1.01 to 3.74 +/- 0.98 nl/(min X mmHg) (P less than 0.05). When the albumin concentration was decreased from low to no albumin the filtration fraction and SNGFR increased even further and were associated with a marked increase in Kf to a value of 27.04 +/- 11.43 nl/min X mmHg). We conclude that there is very little effect of decreases in albumin concentration on Kf until extremely low levels are reached, and at that point there is a marked increase in the ultrafiltration coefficient. Furthermore, when these extremely low concentrations of albumin are reached an important role for albumin in the basic function of the ultrafiltration barrier is demonstrable.
Renal escape from vasopressin: role of pressure diuresis
Authors: Hall J. E. , Montani J. P. , Woods L. L. , Mizelle H. L.
Published: December 2017

This study was designed to examine the role of increased renal artery pressure (RAP) in mediating escape from the antidiuretic action of vasopressin (AVP). In six conscious dogs in which RAP was permitted to increase, AVP infusion, at a rate (0.2 mU X kg-1 X mm-1 iv) that was acutely subpressor, gradually raised mean arterial pressure (MAP) from 97 +/- 2 to 126 +/- 4 mmHg after 5 days while decreasing urine volume and increasing urine osmolality. However, after 4-5 days of AVP infusion, urine volume and osmolality returned to control, and the hypertensive effect of AVP waned so that after 9 days of AVP, MAP averaged only 113 +/- 5 mmHg. In contrast, when RAP was prevented from increasing in seven dogs with a servo-controlled aortic occluder, AVP caused sustained decreases in urine volume and elevated urine osmolality from 609 +/- 27 to 1,160-1,711 mosmol/kg H2O throughout 8 days of infusion. The hypertensive effect of AVP did not wane when RAP was servo-controlled, and after 8 days of AVP infusion, MAP averaged 152 +/- 7 mmHg, compared with a control of 96 +/- 2 mmHg. Servo-controlling RAP also prevented the marked sodium and chloride losses seen with chronic AVP infusion in normal dogs. These findings indicate that escape from the antidiuretic action of AVP is mediated by increased RAP, which causes diuresis and natriuresis, thereby diminishing the hypertensive effect of AVP. However, when pressure diuresis and natriuresis are prevented, AVP causes severe chronic hypertensive, suggesting that AVP could be an important hypertensive mechanism when renal function is impaired.
Contributions of glomerular and tubular mechanisms to antidiuresis in conscious domestic fowl
Authors: Stallone John N. , Braun Eldon J.
Published: December 2017

Pages F842–F850: John N. Stallone and Eldon J. Braun. “Contributions of glomerular and tubular mechanisms to antidiuresis in conscious domestic fowl.” An early version rather than the final version of this article was printed. The corrected article follows.
Angiotensin II inhibition with captopril on plasma ADH, PG synthesis, and renal function in humans
Authors: Usberti M. , Di Minno G. , Ungaro B. , Cianciaruso B. , Federico S. , Ardillo G. , Gargiulo A. , Martucci F. , Pannain M. , Cerbone A. M. , et al.
Published: December 2017

Using captopril (C), an angiotensin (ANG) I converting-enzyme inhibitor, to increase endogenous prostaglandins (PGs) and to decrease endogenous ANG II synthesis, we studied the relationship between endogenous ANG II, PG, and antidiuretic hormone (ADH) release in seven normal volunteers before (control study) and after inhibition of PG synthesis by a single dose of aspirin (ASA study). In the control study, following the administration of 100 mg of C, there was a significant increase of plasma PGE2, plasma-renin activity (PRA), and urinary PGE2 and 6-keto-PGF1 alpha and a decrease of plasma ADH. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were unaffected by C; urine output, fractional sodium excretion (FENa), and osmolal clearance (Cosmol) increased; and urinary osmolality (Uosmol) decreased significantly after C. In the ASA study PG were undetectable in plasma and significantly reduced in urine 1 h after aspirin and did not increase when C was added. Plasma ADH decreased and PRA increased, as in the control study, after C, whereas GFR, RPF, urine output, FENa, Cosmol, and Uosmol were unchanged. These results suggest that the effect of C on ADH release may be mediated, to a large extent, by a fall in endogenous circulating ANG II, since ADH decreased in the presence of both high or undetectable levels of PGE2. The results also suggest that the increase in PGE2 induced by C may precipitate the diuretic and natriuretic effects of acute C administration.
Laser-Doppler determination of papillary blood flow in young and adult rats
Authors: Roman R. J. , Smits C.
Published: December 2017

Renal hemodynamics and renal blood flow autoregulatory ability differ in young (body wt 100 g) and adult (body wt 300 g) rats. Possible age-dependent changes in inner medullary hemodynamics have not been examined because it has not been possible to expose the papilla of adult rats for direct study of the vasa recta circulation. This study presents a technique for exposure of the papilla in any size rat. Seven days before an acute experiment, a small amount of cortical tissue overlying the papilla on the dorsal surface of the kidney was removed. The creation of this papillary window allowed for exposure of the papilla in adult rats after removal of the ureter. Using this preparation, we compared papillary blood flow in young and adult rats using a Periflux differential laser-Doppler flowmeter (Perimed, Stockholm, Sweden). The meter was calibrated by comparing the signal obtained from the papilla of 28 rats with papillary flow measured from the accumulation of 51Cr-labeled erythrocytes in the papilla. The laser-Doppler flow signal was linearly related and highly correlated (r = 0.92) to the red cell flow into the papilla. Comparisons of laser-Doppler flow signals obtained from the papilla of young and adult animals indicated that papillary blood flow was approximately 2-fold greater in the adult rats than in the young animals. This finding was associated with an enhanced maximal urine concentrating ability found in the younger rats. These studies demonstrate the utility of the laser-Doppler flowmeter for the assessment of papillary blood flow and suggest that inner medullary hemodynamics differ in young and adult rats.