bluuebunny/crossref_metadata_2025 huggingface dataset:
Bradykinin increases cytosolic free [Ca2+] in proximal tubule cells
Authors: Aboolian A. , Nord E. P.
Published: December 2017

The role of bradykinin (BK) as a calcium-mobilizing agonist in cells of renal proximal tubule origin was examined. Experiments were performed on confluent cultures of rabbit proximal tubule cells in primary culture and changes in cytosolic free Ca2+ concentration, [Cai2+], were monitored by use of the Ca2+-sensitive fluorescent probe fura-2. Under steady-state conditions, [Cai2+] was 210 +/- 7 nM in a Ca2+-replete medium vs. 135 +/- 5 nM in a medium devoid of Ca2+. Acute challenge with BK resulted in a transient increment in [Cai2+], which peaked at 150% the resting value within 10 s and was independent of medium [Ca2+]. The K0.5 for the process was 2.5 X 10(-10) M. The BK receptor displayed properties of the beta 2-variety. In a Ca2+-free medium 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) blocked the BK-elicited Ca2+ transient in a time- and dose-dependent manner. In contrast to TMB-8, the Ca2+-channel inhibitor, verapamil, was without effect. Prior exposure of cells to ionomycin completely obviated the BK-induced Ca2+ transient. Cells challenged with BK were nonresponsive to subsequent challenge by a second Ca2+-mobilizing agonist, angiotensin II (ANG II). In summary, these data suggest that BK is an extremely sensitive activator of the phosphoinositol transduction pathway in rabbit proximal tubule cells. Furthermore, the heterologous desensitization between BK and ANG II, in terms of elevating [Cai2+], suggests that these two agonists release Ca2+ from a common intracellular store.
Structure of avian loop of Henle as related to countercurrent multiplier system
Authors: Braun E. J. , Reimer P. R.
Published: December 2017

The ultrastructural detail of the avian loop of Henle was examined, and comparisons were made to the loop of Henle of mammalian kidneys. Birds are the only group of vertebrates other than mammals that have the capability of elaborating a urine more concentrated than the plasma. Therefore, a comparison of the principal tubular element responsible for this phenomenon was made. Gambel's quail (Callipepla gambelii) were used as experimental animals. The animals were anesthetized with Inactin, and the kidneys were perfused-fixed in situ. The results show that the transition from the pars recta of the proximal tubule to the thin descending limb of Henle's loop (DLLH) is very abrupt. The upper part of the DLLH appears to be composed of type 2 and the lower part of type 3 epithelia, a condition somewhat similar to mammals. The junctions of the upper portion of DLLH are of the zonula adherens type and those of the lower portion of DLLH are of the macula adherens type. The epithelium of the loop always thickens before the formation of the hairpin turn with the thick descending limb being approximately 15% of the total DLLH. The structure of the avian renal medulla, in particular that of the loop of Henle, appears to parallel quite closely that postulated by the original formulation of the countercurrent multiplier system for the mammalian kidney.
Hemoglobin- and myoglobin-induced acute renal failure in rats: role of iron in nephrotoxicity
Authors: Paller M. S.
Published: December 2017

In ischemic acute renal failure oxygen free radicals may mediate injury. In addition, iron appears to play a critical role in hydroxyl radical formation and lipid peroxidation during reperfusion of ischemic kidneys. To determine whether iron may play a similar role in pigment (heme protein)-induced acute renal failure, we studied the effects of the iron chelator deferoxamine in two experimental models of pigment-induced acute renal failure, intramuscular glycerol injection and intravenous hemoglobin infusion without and with concurrent ischemia in the rat. Intramuscular injection of 50% glycerol (5 ml/kg) caused inulin clearance to fall to 0.13 +/- 0.03 (SE) ml/min (normal value, 1.0–1.2 ml/min). Continuous infusion of deferoxamine beginning at the time of glycerol injection significantly attenuated this renal dysfunction. Deferoxamine-treated animals had an inulin clearance of 0.37 +/- 0.06 ml/min (P less than 0.01). Glycerol injection was also associated with significant lipid peroxidation, measured as renal malondialdehyde content. Deferoxamine-treated glycerol-injected rats had renal malondialdehyde content not significantly different from control animals. In another model of heme pigment-induced renal injury, hemoglobin was infused to produce hemoglobinuria. Inulin clearance 1 h after hemoglobin infusion was significantly reduced to 0.84 +/- 0.5 ml/min (P less than 0.025). Infusion of deferoxamine after hemoglobin prevented the hemoglobin-induced decrease in inulin clearance. Thirty minutes of renal ischemia followed by infusion of hemoglobin resulted in more severe renal dysfunction with inulin clearance of 0.54 +/- 0.08 ml/min. Deferoxamine infused at the time of reperfusion attenuated the fall in glomerular filtration rate after ischemia and hemoglobin infusion:inulin clearance 1.04 +/- 0.07 (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
CaBPr facilitates intracellular diffusion for Ca pumping in distal convoluted tubule
Authors: Bronner F. , Stein W. D.
Published: December 2017

The system of renal Ca transport in the rat is modeled in terms of two classes of processes: a nonsaturable flux that predominates in the proximal tubule, and an active, vitamin D-dependent flux with major expression in the distal convoluted tubule. There transport is against an electrochemical gradient, with much of the efflux probably mediated by the Ca/Mg-ATPase. Calculations of the rate of free Ca diffusion in tubular cells indicate that an unaided flux would be only one-seventy-seventh of that found experimentally. It is suggested that the vitamin D-induced renal calcium binding protein, CaBPr, Mr approximately 28,000, in raising total cellular calcium by three orders of magnitude, increases the transcellular Ca flux and thus the free intracellular Ca ion concentration at the basolateral pole, allowing the Ca/Mg-ATPase to function near its maximum. Analysis of the rate of nonsaturable Ca flux throughout the kidney tubule suggests a paracellular pathway via bulk flow, following water that is driven osmotically. Evaluation of whole animal data in terms of these two classes of calcium fluxes indicates that our model is consistent with experimental observations and assigns a functional role to active calcium transport.
Whole-cell potassium currents in single early distal tubule cells
Authors: Hunter M. , Oberleithner H. , Henderson R. M. , Giebisch G.
Published: December 2017

The apical membrane potassium conductance of amphibian early distal tubules is sensitive to changes in the intracellular pH, with cellular acidification causing a decreased conductance. With the whole-cell patch-clamp technique, we have measured the total potassium conductance of single isolated early distal tubule cells of the frog. With symmetrical potassium gluconate solutions, the whole-cell current was found to be strongly rectifying, with an inward conductance of 12.9 nS (at intracellular pH between 7.6 and 8.0) and an outward conductance of 1.0 nS. The inward current was almost totally inhibited by the addition of 10 mM Ba2+ to the bath solution. The use of pipette solutions with pH between 7.0 and 8.0 showed a positive correlation between intracellular pH and conductance. In contrast, acidification of the extracellular solution caused no significant change in conductance.
Characteristics of the paracellular pathway of rabbit cortical collecting duct
Authors: Warden D. H. , Schuster V. L. , Stokes J. B.
Published: December 2017

The nature of the paracellular pathway of the rabbit cortical collecting duct (CCD) was examined under conditions designed to eliminate all cellular ion transport. Transcellular conductive pathways were blocked by addition of amiloride and Ba2+ to the perfusate. Cl self-exchange was eliminated by removing Cl from the bath solution, and HCO3 transport was eliminated by omitting HCO3 and CO2 from the solutions. The residual transepithelial conductance (GT) and radioisotopic tracer flux under these conditions probably occur via the paracellular pathway. The GT measured in nontransporting CCD bathed in NaCl solutions was 1.1-1.2 mS/cm2. When Na or Cl was replaced by a less mobile ion, the GT decreased by an amount commensurate with the decrease in solution conductivity. The Na-to-Cl permeability ratio determined by NaCl dilution voltages ranged from 0.55 to 0.82. An independent estimate of paracellular selectivity was obtained by comparing the lumen-to-bath tracer rate coefficients for Na (kNa) and Cl (kCl). The ratio kNa:kCl was 0.75. These observations suggest that the paracellular pathway displays a Na:Cl permselectivity not substantially different from the ratio of their mobilities in water (0.65). Additional experiments demonstrated that the summed partial ionic conductances of Na and Cl calculated from the tracer fluxes were in close agreement with the measured GT. We conclude that the paracellular conductance of CCD is nonselective in character and approximately 1-2 mS/cm2 in magnitude.
Potassium-depletion alkalosis in the rat
Authors: Kaufman A. M. , Kahn T.
Published: December 2017

Studies were performed to investigate the role of concomitant chloride depletion in potassium-depletion alkalosis in the rat and the relationship between potassium depletion, plasma bicarbonate (PHCO3), and net acid excretion. 1) Selective potassium depletion (K-DEPL), potassium plus chloride depletion (KCl-DEPL), or selective chloride depletion (Cl-DEPL) was produced by administering a selectively potassium-, potassium and chloride-, or selectively chloride-deficient diet. In K-DEPL and KCl-DEPL rat, PHCO3 increased progressively and similarly during a 38-day period of restriction, whereas net acid excretion was similar and not elevated in either group. Cl-DEPL did not result in alkalosis. Chloride administration without potassium in alkalotic KCl-DEPL rats did not result in a sustained significant decrease in PHCO3. Potassium administration without chloride in alkalotic KCl-DEPL rats decreased PHCO3. Thus concomitant chloride depletion plays a minimal role in the alkalosis produced by dietary-induced potassium depletion. 2) Administration of a chronic acid load to alkalotic K-DEPL rats did not decrease PHCO3, and net acid excretion increased similarly as in normals. In K-DEPL rats after PHCO3 was reduced toward normal levels with acetazolamide, net acid excretion increased sharply above base-line values and PHCO3 increased markedly. Thus the alkalotic K-DEPL rat maintains the ability to excrete a chronic acid load, and a reduction in PHCO3 elicits an increase in acid excretion to restore the initial acid-base condition. These studies suggest that potassium depletion alters the set-point at which the kidney maintains PHCO3.
Kidney epithelial cells express c-sis protooncogene and secrete PDGF-like protein
Authors: Kartha S. , Bradham D. M. , Grotendorst G. R. , Toback F. G.
Published: December 2017

Nontransformed monkey kidney cells (BSC-1 line), used as a model for renal epithelium, were assayed for release of platelet-derived growth factor (PDGF)-like proteins. BSC-1 cells continuously released a mitogenic activity for fibroblasts and a chemoattractant activity for smooth muscle cells, each of which was inhibited 80-90% by an antibody to human PDGF. A cDNA probe for the PDGF B-chain gene (c-sis), but not for the A-chain gene, hybridized to mRNA obtained from growing and quiescent cells. c-sis gene expression and PDGF-like protein secretion were studied in the presence of known growth-regulatory molecules. A secreted BSC-1 cell protein identical to transforming growth factor beta 2 inhibited DNA synthesis in growing cultures and induced marked accumulation of c-sis mRNA without a corresponding increase in the release of PDGF-like activity. Adenosine diphosphate stimulated DNA synthesis in quiescent cultures and enhanced both c-sis expression and release of PDGF-like activity. However, growing and quiescent cells did not express the PDGF receptor gene or exhibit a mitogenic response to authentic PDGF. Thus the PDGF-like protein released by these kidney epithelial cells could contribute to growth control by a paracrine mechanism.
Fluorescent characterization of collecting duct cells: a second H+-secreting type
Authors: Schwartz G. J. , Satlin L. M. , Bergmann J. E.
Published: December 2017

We have used three fluorescent probes to label acid-base transporting cells with specific physiological properties in the rabbit collecting duct. Rhodamine albumin identified cells active in luminal endocytosis; rhodamine peanut agglutinin (PNA) identified cells with apical surface PNA ligands; and 6-carboxyfluorescein (6-CF) diacetate identified cells with alkaline pH or acetazolamide-sensitive esterase activity. More than 90% of all cells identified by PNA or rhodamine albumin selectively concentrated 6-CF. Axial heterogeneity of the identified cells was clearly evident along the collecting duct. In the midcortical collecting duct the predominant labeled cell (108 +/- 15/mm) was positive for PNA and 6-CF. These cells were less prevalent (69 +/- 10/mm) in inner cortical collecting ducts and absent from the outer medullary collecting duct. Cells that labeled only with 6-CF (with no detectable luminal endocytosis or PNA binding) showed the opposite distribution. They were the predominant identified cell in the inner stripe of the outer medulla (126 +/- 20/mm), and were less common in the cortical collecting duct. Because the former segment secretes H+, it was likely that these cells were H+-secreting cells. We used excitation ratio microspectrofluorometry of 6-CF to measure cytosolic pH (pHi approximately 7.2) and found evidence for a basolateral DIDS-sensitive Cl- -HCO3- exchanger and a Na+-independent luminal H+ pump. The previously described endocytic H+-secreting cell was seen at its highest concentration in the outer stripe (39 +/- 6/mm). Finally, 5-10% of identified cells did not stain selectively with 6-CF in cortical collecting ducts (solely endocytic or PNA binding). The function of these latter types could not be established. These studies suggest that the distribution and number of these populations of cells may determine the direction and magnitude of H+ transport along the collecting duct.
Arginine vasopressin promotes growth of rat glomerular mesangial cells in culture
Authors: Ganz M. B. , Pekar S. K. , Perfetto M. C. , Sterzel R. B.
Published: December 2017

Arginine vasopressin (AVP) binds specifically to vascular smooth muscle-like mesangial cells (MCs) and affects contraction. We tested whether this peptide also modulates growth behavior of rat MCs in early subculture (passage 2-5). Subconfluent, serum-starved MCs were exposed to AVP (10(-10)-10(-6) M) in the presence or absence of insulin (5 micrograms/ml). To assess DNA replication, MC uptake of [3H]thymidine (24-h pulse) was determined on days 1, 2, and 3. AVP alone averaged a 1.97-fold increase in DNA synthesis at 24 h, whereas the mean stimulatory effects of AVP at 48 and 72 h were 7.21- and 5.42-fold, respectively. MCs exposed simultaneously to AVP and insulin showed potentiation of the mitogenic response to AVP alone. The V1-receptor antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene proprionic acid), 2-(O-methyl-Tyr)-Arg]vasopressin (PMP) inhibited only AVP-induced promotion of MC growth (maximal inhibition of -78.3%). The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) acutely stimulated MC proliferation but did not add to the AVP effect. Preincubation of MCs with 600 nM of TPA for 48 h significantly inhibited AVP-induced mitogenesis (-87.2%). By use of fura-2, intracellular calcium (Cai) was assessed by spectrofluorometry. The addition of AVP (10(-12)-10(-6) M) led to a rapid, transient, dose-dependent increase in Cai of 154-383%, respectively. The AVP-induced increase in Cai was greatly inhibited by 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester hydrochloride (TMB-8) (10(-8)-10(-6) M), an inhibitor of Cai release (-23.9 to -72.1%), and it was blunted by the atrial natriuretic peptide AP-28 (-38.3%).(ABSTRACT TRUNCATED AT 250 WORDS)
Urinary cGMP as biological marker of the renal activity of atrial natriuretic factor
Authors: Wong K. R. , Xie M. H. , Shi L. B. , Liu F. Y. , Huang C. L. , Gardner D. G. , Cogan M. G.
Published: December 2017

Current evidence suggests guanosine 3',5'-cyclic monophosphate (cGMP) serves as the second messenger for atrial natriuretic factor (ANF) in the kidney in vivo. We examined whether extracellular cGMP accumulation quantitatively reflected the concentration of cGMP within renal cells and whether urinary excretion of cGMP correlated with the physiological action of ANF. cGMP egression was examined in renal epithelial LLC-PK1 cells. ANF augmented intracellular cGMP concentration and extracellular cGMP appearance. Extracellular cGMP was an excellent function of the time-integrated intracellular cGMP concentration. In clearance studies in awake rats, urinary cGMP was primarily of renal cellular origin and correlated with the natriuresis induced by ANF in a time-dependent and concentration-dependent fashion. Urinary cGMP excretion may be useful as a biological marker for the renal activity of ANF in vivo.
Effect of luminal perfusion on glucose production by isolated proximal tubules
Authors: Nagami G. T. , Lee P.
Published: December 2017

The effects of luminal perfusion on glucose production by the proximal tubule were examined by use of the technique of in vitro microperfusion with an ultramicroassay for glucose to measure the net glucose production rates in isolated mouse midproximal tubule segments. Tubules bathed in Krebs-Ringer bicarbonate (KRB) buffer containing L-glutamine and acetate and perfused with KRB buffer at a high flow rate produced glucose at a lower rate (0.12 +/- 0.02 pmol.min-1.mm-1) than unperfused segments (0.40 +/- 0.03) or segments perfused at a lower flow rate (0.24 +/- 0.03). In contrast, the estimated rates of glucose utilization were not affected by luminal perfusion. The inhibition of net fluid reabsorption by perfusion with a modified KRB buffer containing amiloride or by addition of ouabain to the bath medium raised glucose production rates to levels equaling or exceeding those observed in unperfused tubules. The inhibition of glucose production by luminal perfusion occurred in the presence of multiple substrates (i.e., glutamine, acetate, lactate, pyruvate, alanine, and valerate) or nonammoniagenic substrates (i.e., lactate and pyruvate) in the bath medium. Thus net glucose production is inhibited by luminal perfusion and the inhibitory effect is dependent on intact fluid reabsorption. The reduction in net glucose production observed with perfusion does not result from increased glucose utilization and is not dependent on the presence of specific substrates.
Effect of renal perfusion pressure on renal interstitial hydrostatic pressure in rats
Authors: Khraibi A. A. , Haas J. A. , Knox F. G.
Published: December 2017

The purpose of this study was to investigate the hypothesis that changes in renal perfusion pressure may be transmitted to the renal interstitium and cause alterations in renal interstitial hydrostatic pressure and sodium excretion. A method that utilizes a chronically implanted polyethylene matrix that allows for direct continuous measurement of renal interstitial hydrostatic pressure, and agrees well with subcapsular measurement in rats, was developed. Renal interstitial hydrostatic pressure, fractional excretion of sodium, and urine flow rate were 3.0 +/- 0.3 mmHg, 0.35 +/- 0.13%, and 19.44 +/- 3.00 microliter/min, respectively, when renal perfusion pressure was 101 +/- 0.8 mmHg. When renal perfusion pressure was increased to 123 +/- 0.9 mmHg renal interstitial hydrostatic pressure, fractional excretion of sodium, and urine flow rate increased significantly to 5.8 +/- 0.6 mmHg, 1.29 +/- 0.29%, and 50.76 +/- 8.83 microliter/min, respectively, in anesthetized male Sprague-Dawley rats. These changes occur despite a well-autoregulated glomerular filtration rate and renal blood flow. In conclusion, increasing renal perfusion pressure caused a significant increase in renal interstitial hydrostatic pressure as measured directly by the implanted polyethylene matrix method and was associated with a significant increase in sodium excretion.
ANF inhibits NaCl and fluid absorption in cortical collecting duct of rat kidney
Authors: Nonoguchi H. , Sands J. M. , Knepper M. A.
Published: December 2017

Atrial natriuretic factor (ANF) is a peptide hormone that causes a large increase in urinary sodium chloride and water excretion when its plasma concentration rises above basal levels. As yet, there is no consensus regarding the chief site of action of ANF in the kidney. We microdissected and perfused rat cortical collecting ducts in vitro to determine whether ANF-(1-28) can directly inhibit net sodium and fluid absorption. ANF decreased both net sodium absorption and vasopressin-stimulated net fluid absorption by 50-90% when added to the peritubular bath solution. Approximately 50% inhibition of net fluid absorption occurred at 0.1 nM ANF, a level equivalent to plasma concentrations in volume-expanded rats. The action of ANF was mimicked by the addition of exogenous guanosine 3',5'-cyclic monophosphate. If ANF has a similar action on the cortical collecting duct in vivo, it could account for a substantial part of the ANF-mediated increase in urinary sodium and water excretion.
Renal metabolism of the oxidized form of ascorbic acid (dehydro-L-ascorbic acid)
Authors: Rose R. C.
Published: December 2017

We evaluated whether specific transport and metabolic properties exist in rat and guinea pig kidney for handling the immediate oxidative product of ascorbic acid, dehydro-L-ascorbic acid. Isolated tubules were used to measure uptake of 10 microM [14C]-dehydro-L-ascorbic acid over an 8-min incubation period. Uptake did not show dependence on the bathing media electrolyte composition but was inhibited to some extent by glucose. In tubules of both animal species the majority of 14C label present in the tissue extract was in the reduced form. No degredative enzymatic effect on dehydro-L-ascorbic acid is evident. Thirty-six percent of the [14C]dehydro-L-ascorbic acid reduced by the tubules was released during an 8-min incubation. Recently formed ascorbic acid is not substantially bound to cellular components. A factor necessary for dehydro-L-ascorbic acid reduction in renal cortex was found primarily in the 55-70% ammonium sulfate fraction. It is retained by mol wt 12,000 dialysis tubing, is heat labile, pH sensitive, inhibited by thiol reagents, and is most active in the presence of NADPH and glutathione. It has a molecular weight between that of blue dextran and cytochrome c as indicated by gel chromatography. We suggest that a cytosolic enzyme functions in reduction of dehydro-L-ascorbic acid and thereby is important in maintaining the redox state of ascorbic acid derived from the glomerular filtrate or from peritubular fluid.
Role of BBM lipid composition and fluidity in impaired renal Pi transport in aged rat
Authors: Levi M. , Jameson D. M. , van der Meer B. W.
Published: December 2017

Renal tubular phosphate (Pi) transport is impaired in the aged rat. The decrement in Pi transport is manifested as a decrease in the Vmax of the luminal brush-border membrane (BBM) sodium-dependent Pi transport. In the present study we determined the potential role of alterations in cortical BBM lipid composition and fluidity in the age-related phosphaturia observed in rats. In the aged rat there are significant increases in the BBM cholesterol (Chol, 504 vs. 422 nmol/mg protein in adult, P less than 0.01) and sphingomyelin (Sph, 41.8 vs. 37.5 mol% in adult, P less than 0.01) and a decrease in the BBM fluidity [increase in fluorescence anisotropy of diphenylhexatriene (DPH), rDPH, 0.221 vs. 0.215 in adult, P less than 0.01]. The BBM lipid compositional and fluidity alterations may also play an important role in the impaired renal adaptation to a low-Pi diet in the aged rat. In the adult rat the renal adaptation to a low-Pi diet is associated with a decrease in BBM Chol (370 to 307 nmol/mg protein, P less than 0.01) and an increase in fluidity (decrease in rDPH 0.207 to 0.201, P less than 0.05). In the aged rat the renal adaptation to a low-Pi diet is incomplete and is associated with impaired ability to lower BBM Chol (441 to 429 nmol/mg protein, P = NS) and to increase fluidity (rDPH 0.211 to 0.211, P = NS). The results of this study therefore suggest that in the aged rat the increase in BBM Chol and Sph content, and the decrease in BBM fluidity play an important role in the impaired renal tubular Pi transport and adaptation to a low-Pi diet.
Brush-border TEA transport in intact proximal tubules and isolated membrane vesicles
Authors: Dantzler W. H. , Brokl O. H. , Wright S. H.
Published: December 2017

The efflux of the organic cation, tetraethylammonium (TEA), across proximal cell luminal membranes was studied using intact, perfused rabbit proximal tubules and isolated rabbit cortical brush-border membrane vesicles (BBMV). Increases of either the extravesicular H+ concentration (from pH 7.5 to pH 6.5) or the extravesicular concentration of unlabeled TEA (from 0.1 to 0.5 mM) increased the rate of efflux of radioactively labeled TEA from BBMV. Similarly, when proximal tubules were preloaded with labeled TEA and then submerged in a mineral oil bath, a rapid increase in either the H+ concentration (from pH 7.5 to pH 5.8) or the TEA concentration (from 0 to 1 mM) of the tubular perfusate produced an acute increase in efflux of the labeled TEA across the luminal brush-border membrane. These results with intact tubules and isolated membranes are consistent with previous suggestions that TEA transport across the brush border of proximal tubule cells involves a carrier-mediated countertransport process and represent the first demonstration with intact proximal tubules that the secretory flux of TEA occurs by an exchange with H+.
Inner medullary blood flow in postischemic acute renal failure in the rat
Authors: Yagil Y. , Miyamoto M. , Jamison R. L.
Published: December 2017

To study the effect of renal ischemia on the circulation in the inner medulla, blood flow in descending and ascending vasa recta was determined by fluorescence videomicroscopy in the exposed papilla of the uninephrectomized rat after clamping of the renal artery for 45 min. Total renal blood flow was determined in parallel studies with an electromagnetic flowmeter. Animals were studied 90 min (group 1E) and 24 h (group 2E) after right nephrectomy and release of the left renal artery clamp. Control rats were studied 90 min (group 1C) and 24 h (group 2C) after right nephrectomy alone. In groups 1E and 2E, total renal blood flow was reduced to 70 and 80% of that in their respective controls; renal vascular resistance increased by 50 and 73%, respectively. In striking contrast, blood flow was markedly elevated in descending and ascending vasa recta in groups 1E and 2E compared with the values in their respective uninephrectomized controls. These results indicate that the circulation in the inner medulla is rapidly restored after 45 min of total renal ischemia and that vasa recta blood flow rises above normal after 90 min and 24 h, despite a reduction in total renal blood flow and an increase in renal vascular resistance.
Nature of the renal hemodynamic action of amino acids in dogs
Authors: Premen A. J.
Published: December 2017

Anesthetized dogs were used to study the nature of the renal hyperemia and hyperfiltration ascribed to amino acids. Intravenous (n = 6) or intraportal venous (n = 6) infusion of a solution of three metabolizable amino acids [serine, alanine, and proline (SAP) approximately 0.051 mmol.kg-1.min-1] elevated renal blood flow (RBF) and glomerular filtration rate (GFR) by a similar amount (30%) over the same time course (60 min). Yet, direct intra-arterial infusion of SAP into the kidney at either approximately 0.0051 or 0.051 mmol.kg-.min-1 (n = 12) failed to significantly elevate either RBF or GFR over 60 min. A transient increase in RBF (approximately 13%) was, however, noted by minute 15 of the infusion. Unlike SAP, intraportal venous infusion of a physiological dose of branched-chain amino acids (valine, leucine, and isoleucine, approximately 0.0195 mmol.kg-1.min-1, n = 6) failed to elevate either RBF or GFR over 60 min. By comparison, either intravenous or intraportal venous infusion of SAP at approximately 0.020 mmol.kg-1.min-1 (n = 12) elevated renal hemodynamics by approximately 14% over 60 min. The data suggest that the liver does not directly mediate amino acid-induced increases in renal hemodynamics but that some other intermediary step activated following amino acid administration may be necessary before the renal hyperemia and hyperfiltration ascribed to amino acids are manifested in anesthetized dogs.
Reserpine but not surgical denervation regulates rat renal beta-adrenergic receptors
Authors: Fortin T. L. , Sundaresan P. R.
Published: December 2017

The effects of unilateral surgical denervation or reserpine administration on renal beta-adrenergic receptors were examined in rat kidney cortex. The specific binding of [125I]iodocyanopindolol was used to quantitate the beta-adrenoceptors. Denervation had no significant effect on beta-adrenoceptor concentration in denervated compared with contralateral control kidney, 7 days postsurgery. In contrast, reserpine treatment increased beta-adrenoceptor concentration 30% compared with control (P less than 0.05). Tissue norepinephrine levels were depleted to a significant extent with both manipulations. The reserpine effect was investigated further. Reserpine increased both beta 1- and beta 2-adrenergic receptor subtypes to the same extent. The effect of reserpine was primarily on tubular beta-adrenoceptors including those in the proximal tubules; glomerular beta-adrenoceptors were minimally affected by reserpine. Other adrenergic receptor subtypes (alpha 1- and alpha 2-) were also significantly increased by reserpine; however, angiotensin II receptors were not altered, indicating that the reserpine effect was not a general one affecting all membrane receptors. Reserpine treatment increased beta-adrenergic receptor-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) accumulation by 49% over control in the renal cortex. Denervation had no significant effect on cAMP accumulation. Overall, our results suggest that, in addition to sympathetic nerve terminal norepinephrine, other factors may be involved in the regulation of renal beta-adrenergic receptors.
Proximal bicarbonate absorption independent of Na+-H+ exchange: effect of bicarbonate load
Authors: Bank N. , Aynedjian H. S. , Mutz B. F.
Published: December 2017

To study proximal tubule bicarbonate absorption that is not due to the neutral Na+-H+ antiporter, mid to late proximal convolutions of the rat kidney were microperfused in vivo with a sodium-free choline solution containing 10(-3) M amiloride. The average sodium concentration resulting from sodium influx was 12 mM. At such low intraluminal [Na+], 10(-3) M amiloride should have inhibited the Na+-H+ antiporter by greater than 95%. When 25 mM HCO3- was in the perfusion fluid, measured total CO2 absorption was 100 pmol.mm-1.min-1. When luminal [HCO3-] was raised to 50 mM, and blood [HCO3-] was also raised to approximately 50 mM to avoid a transepithelial HCO3- concentration gradient, total CO2 absorption increased to greater than 300 pmol.mm-1.min-1. Thus raising intraluminal HCO3- concentration caused a marked increase in total CO2 absorption even though intraluminal [Na+] was low and amiloride was present. Control perfusions containing 140 mM Na+ yielded total CO2 absorption that was approximately 100 pmol.mm-1.min-1 higher than with the respective sodium-free perfusion solutions. In additional experiments, either DCCD or NEM was added to sodium-free perfusion solutions to inhibit H+-ATPase. These inhibitors reduced Na+-H+ independent total CO2 absorption markedly. Our observations suggest that under physiological acid-base conditions, sodium-independent H+ secretion can account for approximately 50% of total HCO3- absorption in mid to late proximal convolutions. This mechanism is stimulated by an increase in ambient HCO(-3) concentration to a degree that might account for the load-dependency of proximal HCO(-3) absorption in these segments of the proximal tubule.(ABSTRACT TRUNCATED AT 250 WORDS)
In situ hybridization of prepro-epidermal growth factor mRNA in the mouse kidney
Authors: Salido E. C. , Yen P. H. , Shapiro L. J. , Fisher D. A. , Barajas L.
Published: December 2017

The presence of prepro-epidermal growth factor (prepro-EGF) mRNA was studied in the mouse kidney by in situ hybridization using [3H]prepro-EGF cDNA and 35S-labeled prepro-EGF cRNA probes. In addition, anti-EGF serum was utilized to immunolocalize the peptide by the avidin-biotin complex immunoperoxidase method. Both EGF immunoreactivity and prepro-EGF mRNA hybridization were localized to the thick ascending limb of Henle (TAL) and the distal convoluted tubule (DCT), whereas the macula densa was negative. The glomerulus, the proximal portion of the nephron, and the collecting system were negative. Computer-assisted image analysis of the optical density of the autoradiographic and immunocytochemical signals were performed. The medullary TAL expressed significantly less prepro-EGF than the cortical TAL and the DCT.
Anion dependence of taurine transport by rat renal brush-border membrane vesicles
Authors: Zelikovic I. , Stejskal-Lorenz E. , Lohstroh P. , Budreau A. , Chesney R. W.
Published: December 2017

The anionic requirements and the stoichiometric relationships of Na+-taurine cotransport into rat renal brush-border membrane vesicles (BBMV) were evaluated. External Cl- (100 mM) or Br- (100 mM) gradients supported the full overshoot of Na+-taurine symport and yielded similar high-affinity transport systems for taurine uptake. No active uptake of taurine was evident in the presence of external (100 mM) NaF, NaI, Na gluconate, or Na p-aminohippurate (PAH). Na+:taurine stoichiometry was 2.18:1 in the presence of Cl- and 1.60:1 in the presence of Br-. When the external anion gluconate was employed, Na+-dependent taurine uptake was negligible over the whole range of Na+ concentrations examined. Cl-:taurine and Br-:taurine stoichiometries in the presence of external Na+ were 0.97:1 and 0.81:1, respectively. External furosemide (1 mM) or bumetanide (1 mM) did not change taurine accumulation and kinetic parameters. The anionic transport inhibitors 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (5 x 10(-4) M), N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (10(-3) M) and p-chloromercuribenzoate (5 x 10(-4) M) significantly decreased initial rate of taurine uptake by 48, 31, and 31%, respectively. These data suggest that Na+-taurine cotransport into rat renal BBMV is Cl- or Br- dependent and probably operates by means of 2 Na+:1 Cl- or Br-:1 taurine carrier complex. Na+-taurine symport across the rat renal brush-border membrane surface is not affected by diuretics that influence NaCl cotransport but is affected by selected anionic transport inhibitors. An intact anionic binding site may be needed for this translocation process.
Abnormal diurnal rhythm of plasma vasopressin and urinary output in patients with enuresis
Authors: Rittig S. , Knudsen U. B. , Norgaard J. P. , Pedersen E. B. , Djurhuus J. C.
Published: December 2017

The diurnal variation of plasma vasopressin (AVP), urinary excretion rate, urinary osmolality, and serum osmolality was studied twice in 15 patients with enuresis and in 11 age, weight, and sex matched nonenuretic normal subjects. A diurnal rhythm of AVP with constant levels during the day (8 AM-10 PM) and a highly significant increase during the night (10 PM-8 AM) was found in normal subjects. In contrast, enuretics showed a significantly less pronounced nocturnal increase in AVP with significantly lower nocturnal levels than normal subjects. Normal subjects showed a diurnal rhythm in urinary excretion rate reciprocal to urinary osmolality with a low and highly concentrated nocturnal urinary output. In enuretics, however, this normal diurnal rhythm was absent. In conclusion, an abnormal diurnal rhythm of AVP seems to be an important pathophysiological factor in enuresis, explaining the abnormally high nocturnal urinary volume and the low nocturnal urinary osmolality found in these patients.
Mercurial reagents inhibit flow through ADH-induced water channels in toad bladder
Authors: Hoch B. S. , Gorfien P. C. , Linzer D. , Fusco M. J. , Levine S. D.
Published: December 2017

Mercurial reagents inhibit the water permeability of erythrocytes and proximal renal tubule. We examined the effect of two such agents on vasopressin-induced water transport across toad urinary bladder. Water flows were measured in unfixed tissues and in tissues fixed either with N-ethylmaleimide (NEM) or with glutaraldehyde. When added concurrently with 20 mU/ml vasopressin, 1 mM mucosal p-chloromercuribenzene-sulfonic acid (p-CMBS) inhibited water flow within 1 h. p-CMBS also inhibited flow in tissues that had been fixed with mucosal NEM after stimulation with vasopressin. However, p-CMBS did not affect flow in glutaraldehyde-fixed tissues. In contrast, HgCl2 inhibited water flow and urea permeability even in tissues that had been fixed with glutaraldehyde after stimulation with vasopressin. Inhibition was more pronounced when HgCl2 was added to the mucosal rather than the serosal bathing medium and was not reversed by dithiothreitol. HgCl2 did not diminish the frequency or area of luminal membrane aggregates observed by freeze-fracture electron microscopy. HgCl2 also did not affect amphotericin-induced water permeability in glutaraldehyde-treated tissues, suggesting that it did not diminish the permeability of cellular barriers to flow. Our results parallel closely those reported by other investigators for water flow across erythrocytes and proximal renal tubule and suggest that mercurial reagents can directly block the vasopressin-induced water channel. The water channel at the apical membrane of the toad bladder may prove to share structural similarity with that constantly present in erythrocytes and proximal renal tubule.
Hormonal and Na+ effect on renal glutamine uptake
Authors: Welbourne T. C.
Published: December 2017

The flux of glutamine through cellular PDG or extracellular gamma-glutamyltransferase may reflect competition between the membrane glutamine transporter and extracellular hydrolysis. To test this model, kidneys from nonacidotic (NA) and chronically acidotic rats were isolated and perfused with glutamine in a Na+ media and then with a media in which choline replaced Na+. Replacing Na+ abolished the Na+ gradient and completely eliminated the transport of filtered glutamine back into the perfusate. Nevertheless NH4+ production and glutamine utilization remained intact while glutamate accumulated in the extracellular compartments. In the Na+ media, acidotic rat kidneys produced 2.6 times more NH4+ and utilized 1.5-fold more glutamine than their NA counterparts. In the choline media, acidotic rat kidneys had a large drop in NH4+ production but not in glutamine utilization; associated with this was a large glutamate accumulation in the extracellular compartments consistent with flow through the extracellular pathway. To demonstrate the applicability of this model, the role of the adrenals and glucocorticoids in modulating fluxes over these pathways was studied. Kidneys from adrenalectomized acidotic rats exhibited a diminished transport of glutamine, reduced utilization and decreased ammoniagenesis; glutamate accumulation in the extracellular compartment rose consistent with greater flux via the extracellular glutaminase. Supplementing these animals with triamcinolone restored flow into the cellular pathway. The results confirm the in situ activity of two renal glutaminases whose relative contributions to renal ammoniagenesis are dependent on the acid base balance, glucocorticoids, and the existing Na+ gradient.
Effects of luminal Na+ on single Na+ channels in A6 cells, a regulatory role for protein kinase C
Authors: Ling B. N. , Eaton D. C.
Published: December 2017

Na+ "self-inhibition" in tight epithelia describes the reduction in apical Na+ permeability observed with increasing luminal Na+ concentration. Patch clamp was used to examine regulation of self-inhibition at the level of single Na+ channels. After cell-attached patches (pipette solution, 129 mM NaCl) were obtained on amphibian distal nephron cells (A6), the 129 mM NaCl (high Na+) apical bath outside of the patch was replaced with 3 mM NaCl (low Na+). Within minutes there was an increase in open channel probability (Po) and the appearance of one to five "new" channels in patch membranes. A similar increase occurred when apical Na+ entry was blocked by luminal amiloride (10 microM). A23187 (1 microM), a calcium ionophore, added after low Na+ exchange, abolished the rise in channel activity. Increased Po and new channels, induced by either luminal Na+ or amiloride, were also reversed by either 4B-phorbol 12-myristate 13-acetate (PMA; 0.1 microM) or 1-oleyl-2-acetyl glycerol (OAG; 10 microM) over 15-30 min. 4 alpha-Phorbol (0.1 microM), an inactive phorbol, did not reduce channel activity. D-Sphingosine (100 microM), a protein kinase C (PKC) inhibitor, increased Po and new channels. Conclusions: 1) modulation of apical Na+ permeability by luminal Na+ does not require direct interaction of Na+ with the channel protein but, rather, appears to involve an intracellular regulatory pathway, 2) relieving self-inhibition alters both the number and kinetics of single Na+ channels, 3) the effect of low Na+ must be modulated via decreased apical Na+ entry and intracellular Na+, since amiloride yielded similar results, 4) changes in intracellular Na+ probably affect Na+ channel activity via cytosolic Ca2+, 5) the effects of decreasing luminal Na+ are reversed by PKC activators and mimicked by PKC inhibitors suggesting a possible role for PKC in Na+ self-inhibition.
Effect of Ca on Na-D-glucose cotransport across isolated renal brush-border membranes
Authors: Lin J. T. , Xu Z. J. , Lovelace C. , Windhager E. E. , Heinz E.
Published: December 2017

Brush-border membrane vesicles were prepared from rat kidney cortex by Mg precipitation. Using quin2 (free acid), intravesicular [Ca2+] was found to be 44 microM and less than 300 nM when vesicles were incubated in 0.2 mM CaCl2 or Ca-free buffer, respectively. In Ca-loaded vesicles, the initial D-glucose uptake, measured in the presence of 150 mM Na+ and 0.1 mM D-glucose inward gradients, was reduced to 30% of the control uptake. This reduction persisted when the extra-vesicular Ca2+ was chelated by ethylene glycol-bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid but was abolished in the presence of saturating concentrations of D-glucose. Whereas KG0.5 (g) for D-glucose at constant [Na] in the Ca-loaded membranes increased by approximately 50% of the control value (0.5 +/- 0.1 mM), no significant change in Jmax was observed. In contrast, both Jmax and KG0.5 (Na) for glucose, measured as a function of [Na] in the extravesicular fluid, were found to be significantly reduced. Na uptake, determined in the presence of 0.5 mM amiloride, was found to increase by approximately 30% of the value for control membrane. This increase was abolished when vesicles were preincubated with 0.5 mM neomycin or 0.5 mM phlorizin. The results suggest that the effect of Ca2+ on Na entry may be mediated in part by activation of phospholipase C and are consistent with a model of cotransport in which Ca2+ increases the mobility of the binary Na-sugar-translocator complex, thus leading to uncoupling of Na transport from glucose uptake (“slipping”) and in part with Ca-induced Na entry by nonmediated leakage.
Tubuloglomerular feedback activity after glomerular immune injury
Authors: Peterson O. W. , Gushwa L. C. , Wilson C. B. , Blantz R. C.
Published: December 2017

Tubuloglomerular feedback responses were examined in control euvolemic and glomerulonephritic rats 4 wk after administration of antiglomerular basement membrane antibody (AGBM). Single-nephron glomerular filtration rate (SNGFR) was reduced approximately 30% in AGBM rats. Tubuloglomerular feedback responses were also tested with both artificial and native tubular fluid. SNGFR was evaluated at 0, 10, 20, 30, and 40 nl/min. Tubuloglomerular feedback response was present in both control and AGBM rats, although there was a shift in turning point or perfusion rate down and leftward at which SNGFR decreased in the AGBM rats. No difference in tubuloglomerular feedback responses was observed between artificial and native tubular fluids. In this model of moderate glomerulonephritis, tubuloglomerular feedback activity appears to be appropriate and intact, and the composition of the fluid entering the loop of Henle does not appear to determine or to be a condition for the presence or absence of tubuloglomerular feedback activity.
Effects of Cl- transport inhibitors on Cl- permeability across hamster ascending thin limb
Authors: Isozaki T. , Yoshitomi K. , Imai M.
Published: December 2017

The highly conductive Cl- transport pathway exists in the ascending thin limb (ATL) of Henle's loop. To characterize the mechanism of the Cl- conductance across the ATL, we examined effects on Cl- permeability across hamster ATL of Cl- transport inhibitors, including 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), diphenylamine carboxylate (DPC), and anthracene-9-carboxylic acid (9-AC), by the in vitro microperfusion technique. NPPB added to the bath caused reversible suppression of the relative permeability of Cl- to Na+ (PCl/PNa), as estimated from the NaCl diffusion voltage in a dose-dependent manner in a range from 3 x 10(-6) to 10(-3) M. The concentration of NPPB that inhibited PCl/PNa by 50% (ID50) was approximately 3 X 10(-5) M. When 3 X 10(-5) M NPPB was added to the bath, the lumen-to-bath flux coefficient for 36Cl (Kl----b,Cl- 10(-7) cm2/s) was decreased from 130.7 +/- 7.3 to 52.2 +/- 11.6 (n = 7, P less than 0.01). Application of NPPB in the lumen also caused reversible suppression of PCl/PNa, but this effect was less potent compared with the application of the drug via the bath. Whereas 10(-3) M 9-AC or 10(-3) M DPC decreased PCl/PNa by 6.5 +/- 1.2 and 10.2 +/- 2.6%, respectively, 3 X 10(-4) M NPPB decreased PCl/PNa by 69.7 +/- 3.8%. In maleimide-treated tubules, addition of 10(-3) M N-ethylmaleimide (NEM) increased PCl/PNa from 1.0 +/- 0.1 to 1.8 +/- 0.1 (n = 7, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)