bluuebunny/crossref_metadata_2025 huggingface dataset:
Drainage of interstitial fluid from different regions of rat brain
Authors: Szentistvanyi I. , Patlak C. S. , Ellis R. A. , Cserr H. F.
Published: December 2017

Studies were carried out in anesthetized rats comparing dynamics and pathways of interstitial fluid (ISF) drainage from different regions of brain. Rates of drainage from brain and flow into cerebrospinal fluid (CSF) were estimated from the efflux from brain and influx into CSF of radioiodinated albumin (RISA) following microinjection into caudate nucleus, internal capsule, or midbrain: pathways of flow through the subarachnoid space and into lymph were traced from the distribution of horseradish peroxidase and/or Evans blue-labeled albumin after injection into brain. ISF drainage rates (mul X g brain-1 X min-1) estimated for the three injection sites were 0.18, 0.19, and 0.29, respectively. Flow of ISF into bulk CSF sampled from the cisterna magna accounted for 60-75% of efflux from midbrain but only 10-15% of efflux from caudate nucleus or internal capsule. RISA was concentrated in the subarachnoid space, relative to bulk CSF, in sleeves of adventitial tissue surrounding pericerebral arteries, possibly accounting for the low recovery of isotope from bulk CSF. From the subarachnoid space, some fluid drained via olfactory nerve sheaths to retropharyngeal lymph nodes.
Renal excretion of chromium-51 chloride in the dog
Authors: Donaldson D. L. , Smith C. C. , Yunice A. A.
Published: December 2017

To examine the renal handling of the trace element chromium, clearance studies were performed in pentobarbital sodium-anesthetized mongrel dogs following either gavage or intravenous administration of chromium-51(III) chloride. Ultrafilterable plasma chromium-51 comprised as much as 9-19% of the total plasma chromium-51 when the isotope was given by gavage but only 2-3% when given by intravenous infusion. The mean ratio of the clearance of ultrafilterable plasma chromium-51 to that of endogenous creatinine was approximately unity in all dogs [0.97 +/- 0.11 to 1.14 +/- 0.10 by gavage (n = 5); 0.84 +/- 0.05 to 0.97 +/- 0.05 intravenously (n = 4)]. Regardless of the route of administration, ultrafilterable plasma chromium-51 concentration and glomerular filtration rate appeared to be the primary determinants of renal chromium-51 excretion.
Control of glomerular filtration rate: role of intrarenally formed angiotensin II
Authors: Kastner P. R. , Hall J. E. , Guyton A. C.
Published: December 2017

This study was designed to investigate the role of intrarenally formed angiotensin II (ANG II) in controlling glomerular filtration rate (GFR) during reduction of renal artery pressure (RAP). The experimental design prevented renin released by the kidney from entering the systemic circulation and therefore prevented changes in circulating ANG II from influencing GFR control. In dogs with only a functional intrarenal renin-angiotensin system (RAS), GFR and renal blood flow (RBF) were not significantly altered by RAP reduction to 70 mmHg. After blockade of intrarenal ANG II formation with SQ 14225, reduction of RAP to 70 mmHg decreased GFR and filtration fraction to 75.6 +/- 7.0 and 59.0 +/- 4.1% of control, respectively, while RBF remained at 129.3 +/- 8.8% of control. Calculated efferent arteriolar resistance decreased considerably more when RAP was reduced after SQ 14225, whereas preglomerular resistance decreased to about the same level as observed prior to SQ 14225 infusion. After return of endogenously produced ANG II by recirculation of the renal venous blood or after infusion of ANG II (following SQ 14225) at a rate that restored RBF to the control level (with RAP held at 70 mmHg in each case), GFR, filtration fraction, and calculated efferent resistance were restored to control levels, but preglomerular resistance did not change. These results suggest that intrarenal ANG II formation plays an important role in maintaining GFR during reductions in RAP by constricting efferent arterioles.(ABSTRACT TRUNCATED AT 250 WORDS)
Reduced glomerular angiotensin II receptor density in early untreated diabetes mellitus in the rat
Authors: Ballermann B. J. , Skorecki K. L. , Brenner B. M.
Published: December 2017

Density and affinity of glomerular angiotensin II (ANG II) receptors were determined in normal, untreated, and insulin-treated streptozotocin-diabetic rats 3-4 wk after the onset of diabetes mellitus. With low, intermediate, and high salt intake, angiotensin II receptor density varied inversely with the plasma renin concentration (PRC) in normal, insulin-treated, and untreated diabetic rats. PRC values with all three dietary regimens were lower in the untreated diabetic rats when compared with the other groups. Despite lower plasma renin concentration, however, untreated diabetic rats were also found to have significantly lower glomerular ANG II receptor concentrations at all levels of salt intake. On a normal salt intake, glomerular ANG II receptor density was reduced significantly in untreated diabetic rats (853 +/- 74 (SE) fmol/mg protein), compared with insulin-treated diabetic rats (1,185 +/- 118 fmol/mg) and normal controls (1,058 +/- 83 fmol/mg). ANG II receptor affinity did not change with alternations in salt intake or degree of diabetic control. Reduced glomerular ANG II receptor density in the presence of a suppressed renin-ANG II axis may underlie the altered renal vascular responsiveness to ANG II known to occur in diabetes mellitus.
Analysis of the factors influencing peritubular PCO2 in the rat
Authors: Atherton L. J. , Deen W. M. , Maddox D. A. , Gennari F. J.
Published: December 2017

We have developed a mathematical model to assess the relative contributions of several factors to the high CO2 partial pressures observed in rat peritubular capillaries. This model is based on a single nephron and focuses specifically on the CO2 partial pressure differences (delta PCO2) between peritubular capillaries and the afferent arteriole. The model is formulated by writing steady-state mass balances for the glomerulus, proximal tubule, and peritubular capillaries in addition to equilibrium relationships for CO2, HCO3-, blood protein buffers, and hemoglobin carbamino compounds. Principal input parameters include glomerular blood flow rate, rates of HCO3- and water reabsorption, and the rate of metabolic CO2 production. Under conditions representative of normal Munich-Wistar rats, the model predicts delta PCO2 to be 4.1 mmHg, in approximate agreement with experimental observations reported elsewhere. Metabolic CO2 production is responsible for roughly half of this predicted delta PCO2, the remainder being attributable to reabsorption processes. In examining the sensitivity of delta PCO2 to changes in physiological conditions, we consistently found it to be inversely related to glomerular blood flow rate. The influence of changes in HCO3- reabsorption on delta PCO2 is variable and highly dependent on the arterial acid-base status and the ratio of HCO3- reabsorption to water reabsorption.
Regulation of de novo phosphatidylcholine biosynthesis during renal growth
Authors: Hise M. K. , Harris R. H. , Mansbach C. M.
Published: December 2017

Potential regulatory steps of de novo renal cortical synthesis of phosphatidylcholine (PC) were investigated during renal growth in rats. Twenty-four hours following unilateral nephrectomy, cortical PC content was increased in the remaining kidney when compared with sham-operated controls, 3.47 +/- 0.07 and 2.79 +/- 0.14 mumol/mg DNA, respectively (P less than 0.02). No alterations occurred in the cortical PC precursor pools of choline, phosphocholine, cytidine diphosphocholine, or diacylglycerol. At 15 min after the injection of 32P, the incorporation of isotope into the PC pool was increased in the contralateral kidney when compared with sham-operated controls. The calculated maximal velocities of choline kinase and cholinephosphotransferase were increased subsequent to unilateral nephrectomy, supporting a regulatory role for these enzymes in PC biosynthesis during renal growth.
Regulation of proximal bicarbonate reabsorption
Authors: Cogan M. G. , Alpern R. J.
Published: December 2017

Under free-flow conditions, alterations in acid-base and extracellular volume status affect absolute proximal bicarbonate reabsorption. Microperfusion studies have characterized the individual determinants of the active and passive components of proximal acidification. These determinants include luminal bicarbonate concentration, luminal flow rate, peritubular bicarbonate concentration, PCO2, extracellular volume status, and solute-solvent interactions. When these individual determinants are integrated into a computer-simulated model of absolute proximal bicarbonate reabsorption, the results agree well with the in vivo free-flow data.
Interactions of vasopressin, prostaglandins, and cAMP in rat renal papillary collecting tubule cells in culture
Authors: Sato M. , Dunn M. J.
Published: December 2017

To evaluate the hypothesis that prostaglandins (PGs) inhibit vasopressin stimulation of adenylate cyclase in the collecting tubule, we have studied the interactions of vasopressin, PGs, and intracellular cAMP in rat renal papillary collecting tubule (RPCT) cells in cell culture. Inhibition of PGE2 synthesis with acetylsalicylic acid (ASA) did not potentiate arginine vasopressin (AVP)-stimulated intracellular cAMP. Augmentation of prostanoid synthesis with arachidonic acid or exogenous addition of PGE2 did not decrease AVP-stimulated cAMP in the RPCT cells. Arachidonic acid or PGE2, used alone, increased cAMP and ASA reduced cAMP, consistent with the presence of a PG-sensitive adenylate cyclase. Six-hour incubations of RPCT cells produced clear evidence of homologous desensitization of the PGE2 receptor, after exposure to either PGE2 or arachidonic acid, but not heterologous desensitization of the AVP receptor linked to cAMP synthesis. Preincubation of the RPCT cells with AVP or 1-desamino-8-D-arginine vasopressin (dDAVP) induced homologous desensitization of AVP- or dDAVP-stimulated cAMP. Three-day incubations with dDAVP or AVP apparently induced cyclooxygenase activity since PGE2 synthesis increased in response to arachidonic acid and recovery of cyclooxygenase activity after ASA was enhanced by dDAVP or AVP. In conclusion, our data on AVP-stimulated cAMP in cultured RPCT cells do not support the hypothesis that PGE2 inhibits AVP-dependent collecting tubule cAMP.
Mechanism of natriuresis during intrarenal infusion of prostaglandins
Authors: Haas J. A. , Hammond T. G. , Granger J. P. , Blaine E. H. , Knox F. G.
Published: December 2017

Intrarenal infusion of the natural prostaglandin PGE2 increases renal blood flow, renal interstitial hydrostatic pressure, and urinary sodium excretion. A newly synthesized prostaglandin analogue, 4-3-[3-[2-(1-hydroxycyclohexyl)- ethyl]-4-oxo-2-thiazolidinyl]propyl benzoic acid, increases renal blood flow without increasing sodium excretion. To investigate the role of renal interstitial hydrostatic pressure in this dissociation, comparisons were made between PGE2 and the prostaglandin analogue. Intrarenal infusion of PGE2 increased renal blood flow, renal interstitial hydrostatic pressure, and urinary sodium excretion. Following a similar increase in renal blood flow with intrarenal infusion of prostaglandin analogue, renal interstitial hydrostatic pressure and urinary sodium excretion were not changed. To determine whether increases in urinary sodium excretion due to PGE2 infusion are causally related to the increase in renal interstitial hydrostatic pressure rather than to the increase in renal blood flow, responses to PGE2 were obtained in the absence of increases in interstitial pressure. When renal interstitial hydrostatic pressure was held constant, urinary sodium excretion did not change although there was a marked increase in renal blood flow. We conclude that increased renal interstitial hydrostatic pressure is necessary to produce an increase in urinary sodium excretion with prostaglandin-mediated renal vasodilation.
Sheep renal potassium excretion: efferent kaliuretic regulatory factors
Authors: Rabinowitz L. , Sarason R. L. , Yamauchi H.
Published: December 2017

The possibility that efferent factors in addition to aldosterone and plasma K may mediate the renal response to large variations in K intake in sheep was explored in experiments on four mature ewes. K supplementation of a normal diet provided a total K intake of 1,300-1,500 meq/day for 3 days and produced a high K excretion (737 +/- 34 mu eq/min) with plasma K 4.67 +/- 0.07 meq/liter. K deprivation by 83 h of fasting produced low K excretion (48 +/- 10 mu eq/min) with plasma K 3.60 +/- 0.14 meq/liter. Additional treatments during both K-supplemented and K-deprived states included: raising plasma K through the range 4-7 meq/liter by intravenous infusion of 45 meq KCl in 30 min; intravenous infusion of aldosterone (20 micrograms/h) or of an aldosterone antagonist, potassium canrenoate (100 mg/h). Na supplementation during fasting was by rumen infusion of Na acetate-Na propionate (1,000 meq Na/day). Results showed that the increase in plasma K during intravenous K infusion directly elevated K excretion, that aldosterone enhanced and canrenoate depressed the kaliuretic effect of K infusion, and that Na loading during fasting enhanced the kaliuretic effect of aldosterone. Comparisons, made at the same level of plasma K, indicated that differences in plasma K, aldosterone, or Na excretion were not sufficient individually or in combination to account for the large differences of 350-1,150 mu eq/min in K excretion that existed between K-supplemented and K-deprived states. Unidentified kaliuretic regulatory factors appear to play a major role in the homeostatic control of K excretion in sheep under the circumstances of these experiments.
Use of monoclonal antibodies in the study of renal function
Authors: Kashgarian M.
Published: December 2017

Antibodies can be used as highly specific reagents to detect, identify, or purify proteins. Polyvalent antisera directed against transport proteins have been used in a limited number of circumstances to investigate epithelial function. They have a disadvantage in that they are a mixed reagent and require a highly purified antigen in order to be specific. Monoclonal antibodies can be generated with the hybridoma technique and offer the advantage of being a pure antibody derived from a single antibody-producing cell directed at a single antigenic determinant. The methods of generation and screening are described. Monoclonal antibodies have been most frequently used to characterize membrane transport proteins such as Na-K-ATPase and H-K-ATPase. They provide a useful tool for microscopic localization and for probing synthesis, assembly, and insertion of specific proteins. The antigenic composition of nephron segments and polarization of epithelial cells have been studied with these methods. They have a great potential use in studies employing membrane vesicles. Monoclonal antibody technology offers the opportunity to correlate the biochemical, functional, and morphological characteristics of renal tubular epithelial transport.
Interactions between phosphate and oxidative metabolism in proximal renal tubules
Authors: Brazy P. C. , Mandel L. J. , Gullans S. R. , Soltoff S. P.
Published: December 2017

These studies examine the phosphate dependence of fluid absorption and oxidative metabolism in proximal tubules from rabbit kidney. Removal of inorganic phosphate from intraluminal fluid in isolated perfused tubules reduced fluid absorption (Jv) from 1.0 nl X mm-1 X min-1 to zero and removal of phosphate from the medium bathing tubules in suspension reduced O2 consumption rates (coupled, uncoupled, ouabain sensitive, and ouabain insensitive) and ATP contents by 30-40%. Inhibitions induced by removal of phosphate could be altered by addition of selected organic substrates to ambient fluids. Addition of succinate, citrate, or malate preserved uncoupled respiration and partially preserved Jv (0.4-0.9 nl X mm-1 X min-1), with succinate being most effective. Addition of short-chain fatty acids (butyrate or valerate) to phosphate-free media had little or no effect on Jv. n-Butylmalonate, an inhibitor of dicarboxylate anion transport into mitochondria, reduced oxidative metabolism, ATP content, and Jv when added to phosphate-containing media but had no further effect on these tubular functions when added to phosphate-free media. Together these results suggest that phosphate limitation reduces dicarboxylate anion availability to mitochondria and that this inhibition may contribute to the overall reduction in oxidative metabolism and Jv observed under these conditions.
Interactions among renal nerves, prostaglandins, and renal arterial pressure in the regulation of renin release
Authors: Osborn J. L. , Kopp U. C. , Thames M. D. , DiBona G. F.
Published: December 2017

To examine the interactions among the renal nerves, prostaglandins, and renal arterial pressure in the regulation of renin secretion, experiments using low-frequency renal nerve stimulation (LFRNS; supramaximal voltage, 0.5 ms, 0.5 Hz) were performed in anesthetized dogs. LFRNS, which did not affect renal hemodynamics or urinary sodium excretion, increased renin secretion rate before (79 +/- 16 ng/min) but significantly less after renal arterial administration of indomethacin or meclofenamate (26 +/- 7 ng/min). In a separate group of dogs, LFRNS increased both renin secretion rate (266 +/- 139 ng/min) and renal prostaglandin E2 secretion rate (2,080 +/- 635 ng/min). LFRNS does not alter input stimuli to the renal vascular baroreceptor or tubular macula densa receptor mechanisms for renin secretion and represents a direct neural stimulus for renin secretion; this also increases renal prostaglandin E2 secretion rate, which contributes to the increase in renin secretion rate. The renin secretion rate response of innervated and denervated kidneys to reduction in renal arterial pressure to 50 mmHg was examined before and after indomethacin/meclofenamate administration. The observation that indomethacin/meclofenamate decreased but did not abolish the renin secretion rate response to aortic constriction in innervated kidneys suggests the presence of a prostaglandin-independent mechanism that is mediated by an interaction between the renal nerves and the tubular macula densa receptor, as indomethacin/meclofenamate essentially abolished the renin secretion rate response to aortic constriction in denervated kidneys.
Glomerular and postglomerular permselectivity to anionic dextrans in the dog
Authors: Whiteside C. , Silverman M.
Published: December 2017

Glomerular (G) and postglomerular (PG) capillary permselectivity to anionic dextran markers was investigated using the multiple-indicator-dilution (MID) technique in anesthetized mongrel dogs (n = 14). A bolus of solutes that included sulfated [3H]dextran (SO4d) homogeneous fractions 15.0-28.5 A Stokes-Einstein radius, 125I-albumin (plasma reference), [14C]inulin (G reference), and creatinine (interstitial reference) was injected into the left renal artery. Serial samples of left renal venous and urine outflows were rapidly collected. Sulfated [3H]dextran was 100% recovered, indicating no secretion or reabsorption. The urine recovery of the extracellular indicators was a measure of G extraction (EG). Mean EGSO4d/EGi (+/- SD) ranged from 0.82 +/- 0.03 to 0.48 +/- 0.02 for SO4d's 15.0-28.5 A and was invariant with renal plasma flow (F). These values were 30-50% less than the fractional EG for neutral [3H]dextrans. Postglomerular capillary extraction (EPG) was calculated from the renal vein outflow curve upslope ratios. EPGso4d/EPGcreat varied inversely with F, confirming PG diffusion limitation. Mean permeability-surface area (PS) product ratios PSSO4d/PSi (+/- SD) ranged from 0.98 +/- 0.01 to 0.55 +/- 0.04 for SO4d's 15.0-28.5 A and were consistently larger than values for neutral [3H]dextrans of the same molecular size. In contrast to G charge limitation to anionic solute flux, the PG capillaries demonstrate an increase in apparent permeability to anionic relative to neutral dextrans.
Load dependence of HCO3 and H2O reabsorption in the early proximal tubule of the Munich-Wistar rat
Authors: Maddox D. A. , Gennari F. J.
Published: December 2017

Studies were undertaken in Munich-Wistar rats to evaluate the influence of variations in the filtered load of bicarbonate (FLHCO3) and water [single nephron glomerular filtration rate (SNGFR)] on the pattern of reabsorption along the accessible proximal tubule. SNGFR and FLHCO3 were varied by examining animals under conditions of hydropenia, plasma and extracellular volume expansion (VE), and VE plus aortic constriction. Water and HCO-3 reabsorption rates were measured at intervals along the proximal tubule, from very early segments to late segments, and these values compared with previous measurements in euvolemic rats. The earliest accessible portion of the proximal tubule reabsorbed HCO3 and water avidly; 40-55% of FLHCO3 and 18-20% of SNGFR were reabsorbed within the first millimeter. Moreover, when FLHCO3 was increased to as high as 2,400 pmol/min, HCO3 reabsorption rate in the first millimeter of the tubule increased concomitantly, reaching values as high as 1,000 pmol X mm-1 X min-1. In a similar fashion, water reabsorption in the first millimeter increased in direct relation to increases in SNGFR, reaching values as high as 13 nl X mm-1 X min-1 at SNGFR values of 70 nl/min. These results indicate that the early proximal tubule has much higher HCO3 and water reabsorptive rates and a stronger load dependence than has been found in later segments of the proximal tubule. The early proximal tubule thus appears to play a critical role in the maintenance of glomerulotubular balance.
Fluid uptake in the renal papilla by vasa recta estimated by two methods simultaneously
Authors: Zimmerhackl B. , Robertson C. R. , Jamison R. L.
Published: December 2017

Fluid uptake by vasa recta was determined by two independent methods, videomicroscopy and the micropuncture technique, in the exposed papilla of nine antidiuretic rats to reconcile differences in values previously obtained by the two techniques. Erythrocyte velocity (Vrbc) and diameter (D) in descending vasa recta (DVR) (n = 22) and ascending vasa recta (AVR) (n = 31) near the "base" of the papilla were measured. Using a conversion function determined in vitro, Vrbc was transformed into mean blood velocity (Vblood). From D and Vblood, mean blood flow (Q) in DVR and AVR was calculated. In DVR, mean Vrbc, D, and Q were 1.06 +/- 0.01 mm/s, 16.3 +/- 0.4 micron, and 10.6 +/- 1.4 nl/min, respectively. In AVR, each corresponding value differed significantly, 0.47 +/- 0.06 mm/s (P less than 0.001), 19.8 +/- 0.8 micron (P less than 0.001), and 5.65 +/- 1.3 nl/min (P less than 0.025), respectively. Blood samples from DVR and AVR were obtained by micropuncture from the same location. Plasma protein concentration (g/dl) was 5.1 +/- 0.6 in DVR, 4.0 +/- 0.4 (P less than 0.05) in AVR, and 3.6 +/- 0.3 (P less than 0.025) in the renal vein. Assuming no net transcapillary loss of protein, total plasma outflow exceeded inflow by 29%, the excess representing fluid uptake; and to reconcile the blood flow and plasma protein concentrations found, functioning AVR should outnumber functioning DVR by a ratio of 2.1-2.4 to 1, depending on local hematocrit. Given the total number of AVR + DVR = 2,944 (at the base), capillary fluid uptake was calculated to range between 1.5 and 2.6 microliter/min.
Carrier-mediated concentrative urate transport in rat renal membrane vesicles
Authors: Abramson R. G. , Lipkowitz M. S.
Published: December 2017

[2-14C]Urate uptake and efflux were studied in brush border and basolateral membrane vesicles of rat renal cortex that were exposed to 20 microM copper chloride. In the presence of inwardly directed NaCl gradients urate uptake was maintained at levels in excess of chemical equilibrium. Comparison of glucose and chloride uptakes revealed that equilibrium glucose uptake was not affected by copper, but chloride failed to reach equilibrium in copper-exposed vesicles. It is suggested that the persistence of an electrolyte gradient could provide a driving force to raise the concentration of free intravesicular urate above that in the media. Preincubation of vesicles with unlabeled urate failed to diminish uptake of added urate; rather, urate uptake was trans stimulated. Uptake of labeled urate was also significantly accelerated when an outward gradient for unlabeled urate was created. Pyrazinoic and oxonic acids also trans stimulated urate uptake. The demonstration of accelerated homeo- and heteroexchange diffusion indicates that transport is carrier mediated in both brush border and basolateral vesicles. Outwardly directed hydroxyl gradients failed to influence urate uptake in either the presence or absence of copper or NaCl. Thus, this carrier, which is active only in the presence of trace amounts of copper, is distinct from a urate/anion exchanger.
Effect of sustained water diuresis on prostaglandin E2 excretion in humans
Authors: Roberts D. G. , Strife R. J. , Gerber J. G. , Murphy R. C. , Nies A. S.
Published: December 2017

The relationship of the renal excretion of prostaglandin E2 (PGE2) to urine flow during a water diuresis was examined using radioimmunoassay (RIA) and gas chromatography-mass spectrometry (GC-MS). Seven normal women fasted overnight were water loaded with 20 ml/kg orally, and each hour for 3 h they drank water to replace the urine volume plus 20 ml. The osmolality of the collected urines ranged from 49 to 1,073 mosmol/kg. Assay of urinary PGE2 concentrations by both RIA and GC-MS gave a correlation coefficient of 0.94. Eight normal women were then studied with a water diuresis sustained for 6 h. The excretion of PGE2 (measured with the validated RIA) increased for the 1st 2-3 h (from 1.8 +/- 0.5 to 25.8 +/- 16.6 pg X kg-1 X min-1), but then fell to base-line level by the 5th h (to 2.9 +/- 0.8 pg X kg-1 X min-1) even though the water diuresis was sustained. The urinary concentration vs. time curves for PGE2 and for the freely diffusible solute urea were compared. PGE2 concentration remained elevated for 3 h before falling (from the 100 pg/ml range to 15 pg/ml) while urea concentration decreased steadily from the 1st h. This finding suggests that the early urinary PGE2 excretion was not a washout phenomenon and is consistent with a transient increase in PGE2 synthesis. We conclude that urinary excretion of PGE2 is not a simple function of urine flow after a water load. There is a transient initial increase in urinary PGE2 excretion at the start of a water load that probably reflects an increase in renal PGE2 synthesis. However, with a sustained water diuresis, PGE2 excretion falls, indicating that an enhanced PGE2 synthesis rate is not required to sustain a water diuresis.
Importance of the liver during glucagon-mediated increases in canine renal hemodynamics
Authors: Premen A. J.
Published: December 2017

We ascertained the importance of the liver in mediating glucagon-induced increases in renal blood flow (RBF) and glomerular filtration rate (GFR) by comparing the renal hemodynamic responses to intrarenal versus intraportal infusion of glucagon at 3 ng X kg-1 X min-1 (a dose previously considered "physiologic") in two separate sets of anesthetized dogs. Following intrarenal infusion for 60 min (n = 6), glucagon was without effect on RBF and GFR. On the average, RBF and GFR increased by only 2 +/- 1 and 3 +/- 1%, respectively. However, in a second group of dogs (n = 6), intraportal infusion of glucagon significantly increased both RBF and GFR by the same order of magnitude over 60 min. RBF and GFR increased, on the average, by 22 +/- 2 and 20 +/- 2%, respectively. Peak responses occurred 30 min following glucagon infusion when RBF and GFR were elevated by 25 +/- 2 and 26 +/- 2%, respectively. In neither group of dogs were filtration fraction, arterial pressure, heart rate, arterial hematocrit, or arterial plasma protein concentration altered. These data indicate that the liver plays an important role in mediating the renal hyperemia and hyperfiltration observed following a physiologic infusion of glucagon.
Intracellular Cl activity changes of frog skin
Authors: Biber T. U. , Drewnowska K. , Baumgarten C. M. , Fisher R. S.
Published: December 2017

The intracellular Cl activity and potential were determined in short-circuited frog skin with single-barrel microelectrodes. With NaCl Ringer solution on the apical and basolateral side, the intracellular Cl activity was 15.5 +/- 0.5 mM and the intracellular potential was -90 +/- 1.0 mV, indicating that the intracellular Cl activity was above electrochemical equilibrium. When the solution on the apical side was changed to a Cl-free solution (Cl replaced by methanesulfonate), no significant difference was observed in intracellular Cl activity. However, when the skins were Cl-depleted by replacing the NaCl Ringer solution on both sides with a Cl-free solution, the intracellular Cl activity decreased to 1.7 +/- 0.1 mM and the intracellular potential fell to -66.7 +/- 1.3 mV. Addition of Cl (i.e., NaCl Ringer solution) to the apical side of Cl-depleted skins caused a significant increase in intracellular Cl activity to 6.3 mM. This increase was prevented by amiloride (10(-4) M) added on the apical side simultaneously with Cl. Restoration of Cl on the basolateral side of Cl-depleted tissues also raised the intracellular Cl activity to about the same level as when Cl was added on the apical side (6.8 mM). Changes in membrane potential occurred in a delayed fashion over a period of 15 min or more when Cl was added or removed on either side of the skin. The absence of an immediate membrane potential response indicates that Cl conductance is not detectable. We conclude, therefore, that the Cl transfer across the apical and basolateral cell membrane occurs primarily via electroneutral mechanisms.
Reduced renal blood flow in early cisplatin-induced acute renal failure in the rat
Authors: Winston J. A. , Safirstein R.
Published: December 2017

Studies were designed to determine the cause of the reduced glomerular filtration rate (GFR) in early cisplatin-induced acute renal failure. Rats were studied 72 h following a single intraperitoneal injection of cisplatin (5 mg/kg) or vehicle (0.9% NaCl). Whole kidney GFR and blood flow were lower in cisplatin-treated animals than in controls (0.30 +/- 0.06 vs. 1.17 +/- 0.06 ml X min-1 X g kidney wt-1 and 5.30 +/- 0.62 vs. 8.25 +/- 0.43 ml X min-1 X g kidney wt-1, respectively; P less than 0.001), as were superficial nephron GFR and stop-flow pressure (20.2 +/- 2.1 vs. 34.5 +/- 2.0 nl X min-1 X g kidney wt-1 and 29.0 +/- 1.9 vs. 39.8 +/- 1.3 mmHg, respectively; P less than 0.001). After volume expansion, renal plasma flow increased in control rats, whereas whole kidney and single nephron GFR did not change. In experimental animals, whole kidney filtration rate rose to 0.58 +/- 0.07 ml X min-1 X g kidney wt-1, single nephron filtration rate increased to 29.9 +/- 3.5 nl X min-1 X g kidney wt-1 (P less than 0.005), and renal plasma flow increased to 5.62 +/- 0.60 ml X min-1 X g kidney wt-1 (P less than 0.05). Intratubular hydrostatic pressure was not different in the two groups before or after volume expansion. The results of these studies show that the reduced GFR in early cisplatin-induced renal failure is due, in part, to reversible changes in renal blood flow and renal vascular resistance.
Effect of bicarbonate on glutamine and glutamate metabolism by rat kidney cortex mitochondria
Authors: Scaduto R. C. , Schoolwerth A. C.
Published: December 2017

Isolated rat kidney cortex mitochondria were incubated at pH 7.4 in the presence or absence of a CO2/bicarbonate buffer (28 mM) to investigate the pH-independent role of bicarbonate on glutamine and glutamate metabolism. Changes in the concentration of key intermediates and products during the incubations were used to calculate metabolite flux rates through specific mitochondrial enzymes. With 1 mM glutamine and 2 mM glutamate as substrates, bicarbonate caused an inhibition of glutamate oxalacetate transaminase flux and a stimulation of glutamate deamination. The same effects were also produced with addition of either aminooxyacetate or malonate. These effects of bicarbonate were prevented when 0.2 mM malate was included as an additional substrate. Bicarbonate ion was identified as a potent competitive inhibitor of rat kidney cortex succinate dehydrogenase. These results indicate that aminooxyacetate, malonate, and bicarbonate all act to stimulate glutamate deamination through a suppression of glutamate transamination, and that the control by transamination of glutamate deamination is due to alterations in alpha-ketoglutarate metabolism. In contrast, in mitochondria incubated with glutamine in the absence of glutamate, bicarbonate was found to inhibit glutamate dehydrogenase flux. This effect was found to be due in part to the lower intramitochondrial pH observed in incubations with bicarbonate. These findings indicate that bicarbonate ion, independent of pH, may have an important regulatory role in renal glutamine and glutamate metabolism.
Renin secretion and loop of Henle chloride reabsorption in the adrenalectomized rat
Authors: Welch W. J. , Ott C. E. , Guthrie G. P. , Kotchen T. A.
Published: December 2017

Renin release is increased in the adrenalectomized rat and is not inhibited by sodium chloride administration. The purpose of this study was to determine whether increased renin release is related to impaired absorptive chloride transport in the loop of Henle. Chloride transport in the loop was measured before and after acute saline infusion in three groups of rats: 1) saline-drinking adrenalectomized rats (Adx); 2) saline-drinking dexamethasone-treated adrenalectomized rats (Dex); and 3) water-drinking sham-operated controls. Unrelated to differences of arterial pressure, glomerular filtration rate, or net sodium chloride balance, chloride reabsorption in the loop of Henle of Adx [836 +/- 172 peq/min (SE)] was less (P less than 0.01) than in controls (1,646 +/- 353) and Dex (1,377 +/- 318) before saline infusion. After saline infusion, chloride delivery to the loop increased (P less than 0.05) in all three groups. However, loop chloride reabsorption increased (P less than 0.01) only in controls and Dex but not in Adx. Before saline infusion, plasma renin concentration (PRC) of Adx (350 +/- 108 U/ml) was greater (P less than 0.01) than that in controls (56 +/- 6) or Dex (108 +/- 36); sodium chloride infusion failed to inhibit PRC in Adx, whereas PRC was suppressed (P less than 0.01) by saline in Dex and controls. Thus stimulation of renin release in adrenalectomized animals was associated with decreased absorptive chloride transport in the loop of Henle. Dexamethasone normalized loop function and renin responsiveness to sodium chloride.
Effects of synthetic atrial natriuretic factor in the isolated perfused rat kidney
Authors: Murray R. D. , Itoh S. , Inagami T. , Misono K. , Seto S. , Scicli A. G. , Carretero O. A.
Published: December 2017

It is known that atrial extracts (AE) and synthetic atrial natriuretic factor (ANF) can increase glomerular filtration rate (GFR) and electrolyte and water excretion both in vivo and in vitro. It is not clear, however, if ANF-induced increases in filtered load (increased GFR) are required to produce natriuresis and diuresis. We perfused isolated rat kidneys with AE or synthetic ANF at constant pressure in a single-pass system. Extracts of atrial tissue (1 mg/ml) and high concentrations of ANF (31 and 61 ng/ml) significantly increased both GFR and electrolyte and water excretion. During continued infusion of ANF, GFR stabilized at increased levels, but sodium and water excretion continued to increase. After the termination of infusions, GFR and potassium excretion returned to control levels, but sodium and water excretion remained significantly elevated. Infusion of a low concentration of ANF (3 ng/ml) significantly increased sodium and water excretion without changing either GFR or potassium excretion. We conclude that increases in GFR are not a prerequisite for natriuresis and diuresis in response to ANF, but that increases in GFR can potentiate the response. Furthermore, our data suggest that ANF increases potassium excretion only if it increases GFR.
Radiation inactivation studies of renal brush border water and urea transport
Authors: Verkman A. S. , Dix J. A. , Seifter J. L. , Skorecki K. L. , Jung C. Y. , Ausiello D. A.
Published: December 2017

Radiation inactivation was used to determine the nature and molecular weight of water and urea transport pathways in brush border membrane vesicles (BBMV) isolated from rabbit renal cortex. BBMV were frozen to -50 degrees C, irradiated with 1.5 MeV electrons, thawed, and assayed for transport or enzyme activity. The freezing process had no effect on enzyme or transport kinetics. BBMV alkaline phosphatase activity gave linear ln(activity) vs. radiation dose plots with a target size of 68 +/- 3 kDa, similar to previously reported values. Water and solute transport were measured using the stopped-flow light-scattering technique. The rates of acetamide and osmotic water transport did not depend on radiation dose (0-7 Mrad), suggesting that transport of these substances does not require a protein carrier. In contrast, urea and thiourea transport gave linear ln(activity) vs. dose curves with a target size of 125-150 kDa; 400 mM urea inhibited thiourea flux by -50% at 0 and 4.7 Mrad, showing that radiation does not affect inhibitor binding to surviving transporters. These studies suggest that BBMV urea transport requires a membrane protein, whereas osmotic water transport does not.
Tubuloglomerular feedback responses with native and artificial tubular fluid
Authors: Schnermann J. , Schubert G. , Briggs J.
Published: December 2017

Experiments were performed to compare the tubuloglomerular feedback response to native and artificial tubular fluid. The change in early proximal flow rate produced by changes in loop of Henle flow rate was measured in anesthetized rats using micropuncture techniques. Loop perfusion fluid was either an artificial solution with an electrolyte composition similar to that of proximal fluid (ATF) or native tubular fluid (NTF) collected from the late proximal tubule. In control rats, in rats on a low NaCl diet, in rats on restricted food intake, and in acutely saline-expanded rats no differences were detected between ATF- and NTF-perfused nephrons. In rats receiving 10 g NaCl/100 g, diet, responses with ATF and NTF to a flow change from 0 to 15 nl/min did not differ significantly; maximum feedback responses (flow change from 0 to 40 nl/min) were, however, significantly greater with ATF (-25.4%) than NTF (-12.9%). Chloride absorption was not different with the two perfusates. With both ATF and NTF a significant negative correlation was found between maximum responses and NaCl intake, with the slope being steeper with NTF. We conclude that some unidentified constituent of tubular fluid affects maximum feedback responses during very high NaCl intake, but feedback responses to physiological flow rate changes appear to be independent of luminal factors.
Localization of binding sites for alpha-rat atrial natriuretic polypeptide in rat kidney
Authors: Koseki C. , Hayashi Y. , Torikai S. , Furuya M. , Ohnuma N. , Imai M.
Published: December 2017

To determine the intrarenal localization of receptors for atrial natriuretic polypeptide (ANP) in the rat, we performed autoradiography and binding assay by using 125I-labeled alpha-rat ANP (alpha-rANP). Autoradiography at the slice and microscopic level in the kidney and binding assay in isolated glomeruli demonstrated that receptors in the renal cortex were distributed mainly in glomeruli. Although dense silver grains were distributed diffusely both in inner medulla and outer stripe of outer medulla, a marked displacement of the grains was observed only in the inner medulla. Autoradiography at the microscopic level also showed that silver grains were distributed in the renal artery, renal pelvis, and inner medullary collecting tubule (IMCT) prepared by the microdissection method, but not in the arcuate artery, interlobular artery, and afferent or efferent arterioles. Specific binding was demonstrated in the isolated glomeruli and the preparation was rich in fragments of IMCT. Apparent binding affinity (Kd) and receptor density (R) for 125I-labeled alpha-rANP in isolated glomeruli and IMCT were Kd = 3.2 and 21 X 10(-9) M, and R = 320 and 420 fmol/mg protein, respectively. These observations suggest that alpha-rANP has a physiological action on glomeruli and possibly on the inner medullary collecting tubules in addition to the renal artery.
Adenine nucleotide metabolism and mitochondrial Ca2+ transport following renal ischemia
Authors: Arnold P. E. , Van Putten V. J. , Lumlertgul D. , Burke T. J. , Schrier R. W.
Published: December 2017

Mitochondrial Ca2+ accumulation and mitochondrial respiratory dysfunction have been observed after renal ischemia. The present study examined the effects of ischemia and reperfusion on cellular energy production and mitochondrial Ca2+ transport after 50 min of bilateral renal artery and vein clamping in the anesthetized rat. Prior to reflow, tissue ATP and total adenine nucleotide levels were severely reduced. These nucleotide levels recovered towards normal but remained lower than control values throughout 24 h of reperfusion. Energy-linked mitochondrial Ca2+ uptake was unmeasurable, mitochondrial Ca2+ efflux was increased and the mitochondria were unable to maintain a steady-state free Ca2+ concentration prior to reflow. Three hours of reperfusion was associated with a normalization of mitochondrial Ca2+ uptake, release, and steady-state buffering. However, progressive deterioration subsequently occurred in these processes. Thus the mitochondrial Ca2+ accumulation previously observed during the later stages of postischemic reperfusion (3-24 h) is due neither to an increase in the rate of active Ca2+ uptake nor to a decrease in the rate of Ca2+ release. The present results therefore suggest that passive mitochondrial Ca2+ accumulation may occur during the later stages of reperfusion, probably due to a progressive increase in the cytosolic Ca2+ concentration.
Chronic effects of vasopressin on plasma renin activity in sodium-restricted dogs
Authors: Merrill D. C. , Cowley A. W.
Published: December 2017

The effects of chronic (4 days) arginine vasopressin (AVP) infusion were studied in two separate groups of animals: normal Na-restricted dogs with intact renal nerves (n = 8) and renal-denervated Na-restricted dogs (n = 5). Volume expansion during AVP infusion was prevented in these studies with a sensitive servo-controlled cage-scale system. With intravenous AVP infusion (0.36 ng X kg-1 X min-1), plasma AVP levels increased from nearly 3 to 15 pg/ml, whereas total body weight remained unchanged from the control level. In renal-innervated dogs, plasma renin activity (PRA) decreased significantly (P less than 0.05) from control levels of 5.50 +/- 0.61 to an average level of 3.45 +/- 0.76 ng angiotensin I (ANG I) X ml-1 X h-1 on days 1 and 2 of AVP infusion. Thereafter, PRA tended to remain decreased on days 3 and 4, averaging 3.82 +/- 1.02 ng ANG I X ml-1 X h-1, but this was not statistically significant. Urinary Na excretion and balance, however, were not significantly altered during the 4-day AVP infusion period. In renal-denervated dogs, the rise of PRA with Na restriction was 50% that seen in normal dogs. In this group, a transient suppression of PRA was observed on day 1 of AVP infusion from 2.84 +/- 0.75 to 1.46 +/- 0.47 ng ANG I X ml-1 X h-1. Urinary Na excretion increased transiently with a small net Na loss of 4.9 +/- 1.3 meq on day 2 of AVP infusion. No significant changes occurred in average 24-h mean arterial pressure (MAP) in response to AVP in either group of dogs. Thus, in contrast to our previous observations in Na-replete dogs, elevations of plasma AVP within the physiological range result in suppression of PRA, but for periods of no longer than 1-2 days in Na-restricted dogs. This decrease of PRA occurred in the absence of measurable changes in MAP, total body weight, or plasma catecholamines. In addition, this transient AVP-induced suppression of PRA was only partially blunted by prior renal denervation. Finally, in the Na-restricted dog, AVP appears to have minimal or no long-term effects on urinary Na excretion.
Occluding junctions in a renal cell line (LLC-PK1) with characteristics of proximal tubular cells
Authors: Rabito C. A.
Published: December 2017

At confluency, LLC-PK1 monolayers develop a transepithelial electrical resistance of 127 omega X cm2 and a spontaneous electrical potential that very seldom exceeds 1 mV. The monolayer shows a linear current-voltage relation in symmetrical solutions. The total conductance increases linearly with increases in the electrolyte concentration of the bathing solution. These characteristics indicate that the membrane that controls the permeability properties of the monolayer is a single membrane that it does not contain very weakly charged sites and it is sufficiently thick to obey the principle of microscopic electroneutrality. The sodium-to-chloride permeability determined from dilution potentials or from direct measurements of unidirectional Na+ and Cl- flux are 0.30 and 0.38, respectively, almost identical to the ratio obtained in the straight segment of the renal proximal tubule. The steady-state value of the electrical resistance depends on the Ca2+ concentration in the incubation medium with an apparent Km of 0.1 mM. A transitory opening of the occluding junctions results in a more uniform distribution of the Na+-dependent sugar transport system, which is normally confined to the apical membrane of the epithelial cell. This result indicates that the occluding junctions in LLC-PK1 monolayers act as a mechanical barrier, preventing the intermixing of extrinsic as well as intrinsic membrane proteins.
Atrial natriuretic factor inhibits sodium transport in medullary collecting duct
Authors: Sonnenberg H. , Honrath U. , Chong C. K. , Wilson D. R.
Published: December 2017

Characteristics of sodium transport in the inner medullary collecting duct were determined in anesthetized rats before and during intravenous infusion of synthetic atrial natriuretic factor (atriopeptin II). Infusion of the factor was associated with increased sodium delivery and reduced fractional reabsorption in the duct. Increasing delivery to the same extent by KCl infusion had no effect on fractional reabsorption. The results demonstrate that atrial natriuretic factor has a specific inhibitory effect on net sodium transport in this part of the nephron. The mechanism of this inhibition may involve induction of sodium permeability and consequent backflux into the tubular lumen.
Atrial peptides inhibit oxygen consumption in kidney medullary collecting duct cells
Authors: Zeidel M. L. , Seifter J. L. , Lear S. , Brenner B. M. , Silva P.
Published: December 2017

Atrial natriuretic peptides (ANP) stimulate renal Na+ excretion by poorly understood mechanisms, perhaps involving direct inhibition of Na+ transport in the kidney medulla. To examine the effects of ANP on renal cells directly, we prepared highly purified cell suspensions derived from inner and outer medullary collecting duct and thick ascending limb of rabbit kidney and monitored ouabain-sensitive oxygen consumption (QO2). Human ANP diminished QO2 by 27.4 +/- 1.6% (mean +/- SE) in inner medullary collecting duct cells but had no effect in cells derived from outer medullary collecting duct or thick ascending limb. The inhibitory effect of ANP was not additive with either amiloride or ouabain. ANP was without effect in the presence of amphotericin. These results indicate that ANP inhibited Na+ entry in inner medullary collecting duct cells. ANP-mediated inhibition of QO2 was dose dependent (Ki = 5.5 X 10(-10) M) and exhibited selectivity for peptide structure. These results suggest that atrial peptides enhance renal sodium excretion partly by direct inhibition of medullary collecting duct sodium transport.