bluuebunny/crossref_metadata_2025 huggingface dataset:
Antagonists of the antidiuretic activity of vasopressin
Authors: Kinter L. B. , Huffman W. F. , Stassen F. L.
Published: December 2017

Competitive antagonists of the antidiuretic (ADH) activity of vasopressin were first described some six years ago. When studied in vitro, ADH antagonists displace vasopressin from specific renal binding sites and antagonize, in a competitive fashion, vasopressin stimulation of adenylate cyclase and transepithelial water, salt, and urea fluxes. When studied in vivo, the ADH antagonists increase renal water excretion and antagonize, in a competitive fashion, the ADH activity of vasopressin. Marked species heterogeneity is apparent with ADH antagonists in vivo, and inconsistencies between in vitro and in vivo findings within the same species are reported. Other renal responses associated with administration of ADH antagonists include changes in renal hemodynamics and renal salt and urea excretion. The effects on salt excretion appear to be limited to those species in which vasopressin stimulation of epithelial salt reabsorption has been demonstrated. In summary, the role of vasopressin as the principal factor regulating renal water handling is supported by experience with ADH receptor antagonists. However, that experience also indicates the emerging significance of autocoids, and other synergistic factors, to affect ADH receptor/effector mechanisms and to modulate renal ADH responses.
Sex differences in renal hemodynamics in rats
Authors: Munger K. , Baylis C.
Published: December 2017

These studies were designed to investigate sex differences in renal hemodynamics under control conditions and in response to two different cyclooxygenase inhibitors. Studies were performed under anesthesia in males, females, and ovariectomized (OVX) rats and in separate groups of conscious, chronically catheterized male and female rats of a different strain. In the control periods, before cyclooxygenase inhibition, the male kidney was vasodilated relative to the female. Because male and female rats have the same number of glomeruli per kidney, the total vascular resistance per glomerulus is substantially greater in females than males. Cyclooxygenase inhibition in the anesthetized intact female rat produced significant increases in single-nephron glomerular filtration rate, glomerular plasma flow rate, glomerular filtration rate, and renal plasma flow, whereas afferent and efferent arteriolar resistances and renal vascular resistance fell. In contrast, anesthetized male and OVX female rats showed no renal hemodynamic response to cyclooxygenase inhibition. In the absence of anesthesia and recent surgery, intact awake female rats responded similarly to conscious male rats in that neither showed any response to cyclooxygenase inhibition. These data suggest a functional sex difference in both baseline renal hemodynamics and the renal response to cyclooxygenase inhibition, the latter unveiled by surgical stress.
Influence of sodium balance on urinary excretion of immunoreactive kinins in rats
Authors: Barabe J. , Huberdeau D. , Bernoussi A.
Published: December 2017

Antibodies against bradykinin (BK) and its metabolites, namely des-Arg9-BK and des-Phe8,Arg9-BK were raised in rabbits, and specific radioimmunoassays (RIA) for these peptides were developed. Specificity studies showed that each RIA was specific for its antigen, since the cross-reactivities of various kinin-related peptides were less than 1.5%. The lowest concentration of peptide that could be measured in these assays was approximately 60 pg/ml. The antibodies were used to measure concentrations of BK and its metabolites in urine and kidneys of rats maintained on different sodium balance for 5 wk. The results showed that normal rats excrete low quantities of BK (63.78 +/- 2.98 ng/day, 88 determinations). The urinary excretion of des-Arg9-BK averaged 77.69 +/- 5.53 ng/day, whereas the amount of des-Phe8,Arg9-BK is equal to 7.13 +/- 0.42 ng/day. Sodium loading brings about a small decrease in the concentration of BK (45.57 +/- 2.36 ng/day, 76 determinations), whereas sodium depletion significantly increased the excretion of BK (94.23 +/- 5.50, 102 determinations, P less than 0.01) accompanied by no modification of the excretion of metabolites. Regression analysis of the results showed a positive correlation between urinary volume and BK in control and sodium-loaded animals and urinary BK and sodium in the sodium-loaded group. In kidney homogenates, sodium depletion increased not only the concentration of BK (10-fold) but also that of des-Arg9-BK and des-Phe8,Arg9-BK by a factor of four and two, respectively, when compared with normal and sodium-loaded animals. These results support the hypothesis that the renal kallikrein-kinin system may be regulated by corticosteroids.
Aberrant responses to growth-regulatory signals by variant kidney epithelial cells
Authors: Walsh-Reitz M. M. , Feldman R. I. , Toback F. G.
Published: December 2017

Cultures that achieved a higher cell density than expected were noted during study of growth regulation in monkey kidney epithelial cells of the BSC-1 line. Multiplication of the variant cells was accelerated, compared with parental cells, as the cultures approached confluence. Cytogenetic analysis, immunofluorescence antibody reactions with specific monkey serum, isoenzyme analysis, microbiological studies, and lack of growth in soft agar indicated that the variant cells were not a contaminating cell type, lacked new isoenzymes, were free of microbial contamination, and were not transformed. Confluent variant cultures did not respond to a purified growth inhibitor protein produced by BSC-1 cells that inhibits multiplication and reduces cell Na content in subconfluent variant and parental cells. Vasopressin, which is a mitogen for parental cells, was a potent growth inhibitor for confluent cultures of variant cells. Low-K or high-Na media, which stimulate proliferation of parental cells, had no effect on growth of the variant cell line. These results suggest that enhanced multiplication of the variant cells is mediated by altered signal transduction pathways and/or receptors for growth-regulatory molecules.
Hypoproteinemia and recovery from edema in dogs
Authors: Joles J. A. , Koomans H. A. , Kortlandt W. , Boer P. , Dorhout Mees E. J.
Published: December 2017

We studied the effects of hypoproteinemia following 12 days of repeated plasmapheresis and low-protein diet on sodium balance, fluid volumes, and renal hemodynamics in six conscious dogs on 50 mmol sodium intake. Measurements during hypoproteinemia were obtained during a 5-day recovery period starting 20 h after the final plasmapheresis session, with continued low-protein diet. During the plasmapheresis period sodium was retained. Sodium balance became negative on the first recovery day when plasma protein was 29 +/- 1 g/l (control 60 +/- 2 g/l, P less than 0.01), and plasma colloid osmotic pressure (COP) was 9 +/- 1 mmHg (control 22 +/- 1 mmHg, P less than 0.01). Subcutaneous fluid COP was lowered from 14 +/- 1 to 4 +/- 1 mmHg (P less than 0.01). Blood volume, plasma renin activity, and aldosterone were unchanged. Glomerular filtration rate and effective renal plasma flow were slightly reduced (NS), and filtration fraction was unchanged. After a second plasmapheresis period in three of the dogs, plasma protein fell to 26 +/- 1 g/l and COP to 7 +/- 1 mmHg. Now sodium was retained on the first day after stopping plasmapheresis, and renin and aldosterone were high. The next day, when plasma protein was again 29 +/- 1 g/l and COP 8 +/- 1 mmHg, these three dogs were able to completely excrete an infusion of 130 mmol sodium. These data suggest that the level of plasma COP below which dogs on a medium-sodium intake would retain sodium averages 8 mmHg, which is considerably lower than generally thought.
Renin and angiotensinogen gene expression and intrarenal renin distribution during ACE inhibition
Authors: Gomez R. A. , Lynch K. R. , Chevalier R. L. , Everett A. D. , Johns D. W. , Wilfong N. , Peach M. J. , Carey R. M.
Published: December 2017

To define whether intrarenal renin and angiotensinogen synthesis and distribution are affected by angiotensin-converting enzyme (ACE) inhibition, a control group of adult, male Wistar-Kyoto rats (n = 7) was compared with a group of rats treated with enalapril (n = 8) for 5 days. Kidney renin and angiotensinogen mRNA levels were detected by Northern and dot blot analysis, using full-length rat renin and angiotensinogen cDNAs. Renin mRNA levels in the enalapril-treated group were 4.6-fold higher than in the control group (P less than 0.05). Angiotensinogen mRNA levels were not significantly different. The intrarenal distribution of renin assessed by immunocytochemistry was markedly different between the two groups of rats. Whereas in the control kidney renin was localized in a juxtaglomerular position, in the kidneys from enalapril-treated rats, renin immunoreactivity of the afferent arteriole extended well beyond the juxtaglomerular loci in the direction of the interlobular artery. The percent of afferent arteriolar length immunostained for renin was higher in the enalapril-treated (53 +/- 17%) than in the control (33 +/- 15) group. Similarly, the ratio of immunostained juxtaglomerular apparatuses (JGA) over total number of JGA and the ratio of immunostained arteries over total number of arteries were higher in the enalapril-treated (0.84 +/- 0.017; 0.68 +/- 0.03) than in the control (0.67 +/- 0.034; 0.43 +/- 0.045) group (P less than 0.05). We conclude that chronic ACE inhibition enhances intrarenal renin synthesis and increases renin expression upstream from the glomerulus and in new sites in blood vessels.(ABSTRACT TRUNCATED AT 250 WORDS)
Renal metabolism of atrial natriuretic peptide in the rat
Authors: Berg J. A. , Hayashi M. , Fujii Y. , Katz A. I.
Published: December 2017

The purpose of this study was to identify the nephron and cell sites involved in the renal metabolism of alpha-rat atrial natriuretic peptide (alpha-rANP) and to examine the degradation products of the peptide. In micro-dissected nephrons 125I-labeled ANP degradation rate was highest in proximal convoluted (PCT) and straight tubules and lowest in glomeruli and papillary collecting tubules, indicating that the sites of ANP degradation and of the receptors that mediate its biological activity in the nephron do not coincide. Among subcellular fractions of cortical homogenates, the luminal membranes were the most active in metabolizing ANP. In contrast, ANP degradation by isolated basolateral membranes was negligible, and the basolateral uptake route in intact tubules did not contribute significantly to its catabolism. Cortical homogenates, luminal membranes, and isolated PCT degraded ANP without evidence of saturation up to pharmacological concentrations (10(-6) M) of the peptide. A major intermediate metabolite was rapidly formed by luminal membranes and was identified with use of a sequence and compositional analysis. This metabolite had the same amino acid sequence as ANP with a cleavage at position Cys7-Phe8, and the disulfide bridge was preserved. These results demonstrate a rapid degradation of ANP by kidney tissue and suggest that the luminal membrane of the proximal tubule is a major nephron site of ANP catabolism.
Differentiation of Na+-K+ pump in rat proximal tubule is modulated by Na+-H+ exchanger
Authors: Fukuda Y. , Aperia A.
Published: December 2017

This study examines the effect of in vivo modulation of Na+-H+ exchange activity on the development of Na+-K+-ATPase in rat kidney proximal convoluted tubule (PCT) segments. To stimulate Na+-H+ exchanger (major entry pathway for Na in PCT), weanling rats were fed NH4Cl for 4 days to induce metabolic acidosis (MA). In vehicle (Vh)-fed rats PCT Na+-K+-ATPase activity (pmol Pi.mm tubule-1.h-1 +/- SE) increased from 481 +/- 78 at 16 days to 1,122 +/- 119 at 20 days. In 20-day-old chronic MA rats, PCT Na+-K+-ATPase activity was 1,717 +/- 109, i.e., significantly higher (P less than 0.01) relative to controls. Chronic MA had no effect on PCT Mg ATPase activity and on Na+-K+-ATPase in the medullary thick ascending limb (MTAL). To inhibit the Na+-H+ exchanger, weanling rats received amiloride (30 micrograms.100 g body wt-1.day-1) via osmotic minipump for 4 days. In Vh-treated rats PCT Na+-K+-ATPase increased from 481 +/- 78 at 16 days to 1,428 +/- 81 at 20 days. In rats given chronic amiloride, PCT Na+-K+-ATPase was significantly lower (858 +/- 75) at 20 days relative to controls but PCT Mg ATPase and MTAL Na+-K+-ATPase activity was the same as in controls. Chronic MA and amiloride had no significant effect on PCT Na+-K+-ATPase activity in adult rats. Acute MA and acute amiloride injection had no significant effect on PCT Na+-K+-ATPase in weanling rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Stimulatory effects of neuronally released norepinephrine on renin release in vitro
Authors: Matsumura Y. , Kawazoe S. , Ichihara T. , Shinyama H. , Kageyama M. , Morimoto S.
Published: December 2017

Extracellular high potassium inhibits renin release in vitro by increasing calcium concentrations in the juxtaglomerular cells. We found that the decreased response of renin release from rat kidney cortical slices in high potassium solution (20-80 mM) changed to a strikingly increased one in the presence of nifedipine at doses over 10(-6) M. We then examined the stimulatory effect of extracellular high potassium in the presence of nifedipine on renin release. The enhancement of release was significantly suppressed either by propranolol or by metoprolol but not by prazosin. High potassium plus nifedipine-induced increase in renin release was markedly attenuated by renal denervation. The enhancing effect was not observed when the slices were incubated in calcium-free medium. Divalent cations such as Cd2+, Co2+, and Mn2+ (0.1-3.0 mM) blocked this enhancement in a concentration-dependent manner. High potassium elicited an increase in 3H efflux from the slices preloaded with [3H]norepinephrine. The increasing effect was not influenced by nifedipine but was abolished by the removal of extracellular calcium or by the addition of divalent cations. These observations suggest to us that the high potassium plus nifedipine-induced increase in renin release from the slices is mediated by norepinephrine derived from renal sympathetic nerves and that this neuronally released norepinephrine stimulates renin release via activation of beta-adrenoceptors.
Accumulation of major organic osmolytes in rat renal inner medulla in dehydration
Authors: Gullans S. R. , Blumenfeld J. D. , Balschi J. A. , Kaleta M. , Brenner R. M. , Heilig C. W. , Hebert S. C.
Published: December 2017

Osmotically active organic solutes, osmolytes, exist at high concentrations in the renal inner medulla; however, their modulation during antidiuresis remains largely undefined. Renal osmolyte levels were measured by nuclear magnetic resonance spectroscopy and biochemical assays in perchloric acid extracts from normal and dehydrated (3 days) rats. Dehydration increased urine osmolality from 1,503 to 3,748 mosmol/kg and inner medullary urea content from 2,036 to 4,405 nmol/mg protein. In addition, inner medullary trimethylamines [glycerophosphorylcholine (GPC) and betaine] and polyhydric alcohols (inositol and sorbitol) significantly increased by 95 and 78%, respectively. Ninhydrin-positive substances (amino acids), although abundant, were unchanged. Renal cortex also contained GPC, betaine, and inositol but only inositol increased with dehydration. Analysis of correlations among inner medullary osmolytes showed that only GPC was consistently elevated by dehydration and was not directly correlated with the other osmolytes. In contrast, betaine and inositol contents were linearly related to each other and both tended to rise only when sorbitol content was unchanged. In conclusion, the major osmolytes in the rat renal inner medulla can increase during antidiuresis but they are regulated in a complex manner.
Glomerular uracil nucleotide synthesis: effects of diabetes and protein intake
Authors: Cortes P. , Dumler F. , Paielli D. L. , Levin N. W.
Published: December 2017

The biosynthesis of uridine 5'-triphosphate (UTP), uridine 5'-diphosphohexoses, and 5'-diphosphohexosamines (UDP-sugars) was studied in isolated rat glomeruli 48 h after streptozotocin-induced diabetes. Compared with control, diabetic glomeruli demonstrated an increase in the following: exogenous orotate utilization, orotate incorporation into UTP and UDP-sugars, UTP accretion rate, and UDP-sugar pool size. Since these phenomena were not associated with enhanced biosynthesis of orotate de novo, the increased glomerular UDP-sugar bioavailability in diabetes is due to enhanced utilization of exogenous orotate. Plasma concentrations of orotate and uridine were measured in control, sham operated, and unilaterally nephrectomized rats receiving 5, 20, or 60% protein diets. The concentration of pyrimidine precursors correlated directly with protein intake, with doubling at the 60% dietary protein level. In conclusion, glomerular uracil ribonucleotide biosynthesis may be modulated by the quantity of dietary protein. Because UDP-sugars are necessary for basement membrane material formation, an increase in their bioavailability may be part of the metabolic change responsible for diabetic glomerulosclerosis. Diets with high protein content could augment this metabolic alteration.
Captopril augments the renal response to an amino acid infusion in diabetic adults
Authors: Slomowitz L. A. , Hirschberg R. , Kopple J. D.
Published: December 2017

This study examined whether patients with insulin-dependent diabetes mellitus and normal renal function have an altered response to an amino acid infusion when they are pretreated with a converting-enzyme inhibitor. Three groups of adults received amino acid infusions for 20 min on two occasions separated by a 240-min interval. Groups 1 (6 normals) and 2 (6 diabetics) ingested captopril (12.5 mg) 120 min before starting the second infusion. Group 3 (4 diabetics) did not receive captopril. Diabetics had normal base-line renal plasma flow, as indicated by para-aminohippuric acid clearance (CPAH), and glomerular filtration rate (GFR). In group 1, the maximum increase in CPAH was significant and similar with both infusions, 23 +/- 5 vs. 15 +/- 3% (SE); maximal changes in GFR were also significant and similar, 20 +/- 5 vs. 20 +/- 6%. In Group 2, the maximal increase in CPAH and GFR with the first infusion was 28 +/- 7 and 23 +/- 6%, respectively. After captopril, the increases in CPAH and GFR were significantly greater than with the first infusion (64 +/- 8%, P less than 0.002, and 67 +/- 9%, P less than 0.002, respectively). In Group 3 diabetics, there was no difference in either CPAH or GFR with the first vs. the second infusion. Thus captopril enhances the renal hemodynamic response to an amino acid load in diabetic patients but not in normal adults.
Quantitative analysis of aldosterone's role in potassium regulation
Authors: Young D. B.
Published: December 2017

Aldosterone is part of a complex system that regulates plasma potassium concentration by affecting the renal excretion of the ion as well as its distribution within the body. Because there are other components of the system, it has been difficult to determine the physiological significance of aldosterone in potassium regulation by attempting to study the hormone's effects in isolation. In this presentation a quantitative analysis of the potassium control system is used to provide information concerning the physiological role of aldosterone in potassium regulation under normal and pathological conditions, as well as during pharmacological interventions.
Cyclic guanosine monophosphate increases hydraulic conductivity in rabbit and rat CCT
Authors: Dillingham M. A. , Anderson R. J.
Published: December 2017

Although guanosine 3',5'-cyclic monophosphate (cGMP) is present in renal nephron segments, there is no information on the role of cGMP as a mediator of renal tubular transport events. We found that an activator of guanylate cyclase (nitroprusside) and 8-bromocGMP (8-BrcGMP) significantly increased hydraulic conductivity in rabbit and rat cortical collecting tubules (CCT) perfused in vitro. The effect of 10(-4) M 8-BrcGMP to increase CCT hydraulic conductivity was reversible and comparable in magnitude and time course to that produced by maximal concentrations of arginine vasopressin. In rabbit CCT, cGMP increased hydraulic conductivity in the presence of phosphodiesterase inhibition with methylisobutylxanthine and in the presence of supramaximal concentrations of arginine vasopressin. Neither nitroprusside nor 8-BrcGMP stimulated adenylate cyclase activity in microdissected CCT. These data demonstrate that cGMP can act independently of either stimulation of adenylate cyclase activity or inhibition of phosphodiesterase activity to increase hydraulic conductivity in the mammalian CCT.
Age-related changes in body fluid volumes in young spontaneously hypertensive rats
Authors: Von Dreele M. M.
Published: December 2017

We have measured total body water (TBW, by dessiccation), extracellular fluid volume (ECF, Na2(35)SO4 space), and plasma volume (PV, radioiodinated serum albumin space) in 5-sec-butyl-5-ethyl-2-thiobarbituric acid and sodium salt (Inactin)-anesthetized spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats aged 12-60 days. Interstitial fluid volume (ISF) was calculated as ECF minus PV. Changes in TBW, ECF, and ISF were largely a function of age in both strains, which is typical of developing mammals. Further analysis revealed that although these volumes were significantly larger in SHR before 25 days of age, after 30 days no difference existed between the strains. Before 25 days of age, when SHR's TBW was expanded, no weight difference was seen between the strains. However, once TBW was normalized (after 30 days), WKY was significantly heavier than SHR. The ISF volume was preferentially enlarged in SHR, although PV was also periodically greater. ISF normalized at the time when blood pressure becomes significantly higher in SHR, when (as we have previously reported) plasma aldosterone falls to WKY values in SHR and when renal function is approaching adult levels. Thus the return of ECF (ISF) to normal values may be a result of decreased aldosterone-dependent volume retention or to diuresis induced by increasing blood pressure in an animal whose renal function is close to maturity.
Response of the renin-angiotensin system to relief of neonatal ureteral obstruction
Authors: Chevalier R. L. , Gomez R. A.
Published: December 2017

Chronic partial ureteral obstruction (CPUO) causes an increase in renal vascular resistance (RVR) that can be prevented by angiotensin II (ANG II)-converting enzyme inhibition. To assess the early effects of CPUO, guinea pigs subjected to neonatal left ureteral obstruction were anesthetized at 11-13 days of age for measurement of cardiac output and renal blood flow (RBF) using radioactive microspheres. Although RBF of the hydronephrotic kidney was not decreased at this age, that of the intact kidney more than doubled (P less than 0.01). To evaluate the hemodynamic response to relief of 5 or 10 days of neonatal left CPUO, animals were studied at 19-28 days of age. Although chronic enalapril maleate administration (30 mg.kg-1.day-1) did not further reduce the ratio of RVR to total vascular resistance (TVR) of the postobstructed kidney, it lowered RVR/TVR of the intact contralateral kidney by 40% (P less than 0.05). Renal renin content [RRC, pg angiotensin I (ANG I).mg protein-1.h-1] was twofold higher in both kidneys of animals with unilateral CPUO compared with those of sham-operated guinea pigs (P less than 0.03), and relief of obstruction normalized RRC. The rise in RVR/TVR resulting from ANG II infusion was not different in left kidneys of sham, CPUO, and CPUO-relief groups. However, for the intact kidney of animals with contralateral relief of CPUO, the increase was greater than in remaining groups (P less than 0.05). We conclude that by reducing intrarenal renin, relief of neonatal unilateral CPUO decreased ANG-mediated vasoconstriction of the postobstructed kidney and increased the vasoconstrictor response of the intact kidney to ANG II.
Tonic inhibition of renal response to vasopressin by a pertussis toxin substrate
Authors: Jeffries W. B. , Fallet R. , Gong G. D. , Van Dreal P. , Pettinger W. A.
Published: December 2017

The putative role of the inhibitory guanine nucleotide binding protein (Gi) in modulating the renal response to vasopressin was investigated using islet activating protein (IAP). IAP treatment in rats in vivo abolished the capacity of alpha 2-adrenoceptors to reverse vasopressin-induced adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in microdissected cortical collecting tubule (CCT) segments. IAP pretreatment also caused a marked upward shift in the dose-response curve of vasopressin (10(-10) to 10(-4) M)-induced cAMP accumulation. Augmentation of the response to vasopressin in rat CCT was dependent on the in vivo dose of IAP and paralleled the loss in alpha 2-adrenoceptor responsiveness. In the isolated perfused kidney the antinatriuretic and antidiuretic effects of the V2-receptor agonist desamino-8-D-arginine vasopressin (DDAVP) (1 pM) were enhanced following IAP pretreatment. alpha 2-Adrenoceptor stimulation (30 nM epinephrine) inhibited the renal effects of DDAVP (1 pM) in kidneys from control but not IAP-pretreated rats. Interestingly, IAP pretreatment alone caused increased urine flow rate and enhanced excretion of sodium and chloride without affecting potassium excretion or renal hemodynamics in vitro. Our results suggest that an IAP substrate, probably Gi, 1) is required for signal transduction by renal alpha 2-adrenoceptors, 2) may tonically modulate the response to vasopressin in the CCT but not of parathyroid hormone in the proximal convoluted tubule, and 3) participates in renal water and electrolyte reabsorption independent of exogenous adenylate cyclase stimulation.
Adaptation of distal tubule and collecting duct to increased sodium delivery. I. Ultrastructure
Authors: Kaissling B. , Stanton B. A.
Published: December 2017

We examined the effects of a chronic increase in tubular sodium delivery on the structure of the distal convoluted tubule (DCT), connecting tubule (CNT), and cortical collecting duct of male Sprague-Dawley rats. Furosemide (12 mg/day) was administered by osmotic minipump for 6 days to increase the rate of sodium delivery to these segments and thereby stimulate sodium uptake. To prevent volume depletion, the furosemide-treated animals were given a drinking solution containing 0.8% NaCl and 0.1% KCl. Control animals were given vehicle (0.9% NaCl) by osmotic minipump and they drank tap water. Furosemide dramatically increased urinary fluid and sodium excretion and decreased urine osmolality threefold vs. control. Furosemide treatment was associated with an increase in epithelial volume of DCT cells, CNT cells, and principal cells and an increase in the basolateral membrane area and mitochondrial volume of each cell type. These alterations in cell structure were not related to changes in plasma aldosterone, glucocorticoid, or arginine vasopressin levels. We conclude that an increase in cell sodium uptake regulates the ultrastructure of the distal tubule.
In vivo generation of hydrogen peroxide by rat kidney cortex and glomeruli
Authors: Guidet B. R. , Shah S. V.
Published: December 2017

The purpose of this study was to demonstrate in vivo generation of hydrogen peroxide by rat renal cortex and glomeruli. Aminotriazole irreversibly inactivates catalase only in the presence of hydrogen peroxide, and previous studies have shown that aminotriazole-mediated inhibition of catalase is a measure of in vivo changes in the hydrogen peroxide generation. Aminotriazole injected intraperitoneally caused a dose-dependent (0.1-1 g/kg) and a time-dependent (15, 30, 60, 90, 120 min) inhibition of the catalase activity in renal cortex. We confirmed that catalase inactivation by aminotriazole was due to formation of a catalase-hydrogen peroxide intermediate (compound I) because catalase inactivation was prevented by ethanol (2 g/kg), a competitive substrate for compound I. The specific activity of catalase in the glomeruli [0.27 +/- 0.026 k/mg protein (where k is the first-order reaction rate constant), n = 5] was significantly lower than the specific activity in the tubules (1.04 +/- 0.15 k/mg protein, n = 5) obtained from the same rats. The residual catalase activity (RCA) in the glomeruli (0.05 +/- 0.01 k/mg protein) was 19% of control values at 90 min after aminotriazole injection (1 g/kg). Taken together these data provide evidence for in vivo generation of hydrogen peroxide by rat renal cortex and glomeruli under normal conditions. Aminotriazole-mediated inhibition of catalase has been used in previous studies as a measure of in vivo changes in the hydrogen peroxide generation.(ABSTRACT TRUNCATED AT 250 WORDS)
PGI2 is not a major prostanoid produced by cultured rabbit renal microvascular endothelial cells
Authors: Chaudhari A. , Pedram A. , Kirschenbaum M. A.
Published: December 2017

The microvasculature is known to be a source of a number of vasoregulatory prostanoids. In the kidney, these prostanoids have been proposed to influence vascular, tubular, and glomerular function. A rapid method for isolation of large numbers of preglomerular renal microvessels (interlobular arteries and afferent arterioles) from the rabbit kidney has recently been developed in this laboratory. In the current report, we describe methods to culture endothelial cells derived from these isolated renal microvessels. Endothelial cells in primary and continuous cultures were grown in monolayers on culture dishes and plates. These cells demonstrated morphology consistent with that described for other endothelial cells in culture including the presence of Weibel-Palade bodies as seen by electron microscopy. The presence of factor VIII immunofluorescence and angiotensin converting-enzyme activity was also observed. The cultured endothelial cells synthesized a number of common prostanoids under in vitro conditions and the hierarchy of biosynthesis was PGE2 greater than PGF2 alpha greater than PGI2 greater than TxA2. The ratio of the in vitro biosynthesis of PGI2:PGE2 was approximately 1:5, as compared with a 3-5:1 ratio seen in freshly isolated intact microvessels. Prostanoid biosynthesis increased in the cultured endothelial cells in the presence of arachidonic acid (1 and 10 microM), A23187 (10 microM), thrombin (5 U/ml), or bradykinin (1 microM) and decreased with mepacrine (10 microM)-or indomethacin (100 microM), suggesting that these cells were metabolically responsive to a variety of prostanoid stimulators and inhibitors. In summary, endothelial cells can be cultured from freshly isolated preglomerular renal microvessels and have the ability to produce a number of vasoregulatory prostanoids under in vitro conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Potassium secretion by the cortical collecting tubule: effect of C1 gradients and ouabain
Authors: Wingo C. S.
Published: December 2017

In various epithelia K and Cl transport are molecularly coupled and KCl cotransport is dependent on the Na-K pump. The present study examines 1) the effect of a bath-to-lumen Cl gradient on K secretion during active Na transport and 2) the effect of basolateral ouabain on K secretion and Na absorption in the presence and the absence of a bath-to-lumen Cl gradient. Under symmetrical conditions there was significant K secretion (JK = -24.0 +/- 3.9 pmol.mm-1.min-1) and Cl secretion (JCl = -15.7 +/- 3.7 pmol.mm-1.min-1). Transepithelial voltage (VT) was significantly lumen negative (-25.3 +/- 5.9 mV), and Cl secretion occurred against its electrochemical gradient by a transcellular mechanism. Increasing bath [Cl] did not hyperpolarize VT; in fact there was a tendency for VT to depolarize and K secretion was not stimulated. However, ouabain significantly inhibited active Cl secretion and net Na absorption both in the presence and absence of a bath-to-lumen Cl gradient. Furthermore, ouabain totally inhibited K secretion in the absence of external ion gradients but inhibited K secretion by only 50% in the presence of a bath-to-lumen Cl gradient. This ouabain-insensitive K secretion exhibited a codependence on Cl secretion. Thus K secretion may occur passively, utilizing Cl movement down its electrochemical gradient when active Na transport is inhibited by ouabain. The results are compatible with the presence of a Cl-linked K-secretory process in the rabbit CCT.(ABSTRACT TRUNCATED AT 250 WORDS)
Does the ultrafiltration coefficient play a key role in regulating glomerular filtration in the rat
Authors: Oken D. E.
Published: December 2017

Various experimental maneuvers, hormones, and pharmacological agents are reported to exert their effects on glomerular filtration largely or exclusively by changing the ultrafiltration coefficient (Kf) of the filtration barrier. In light of a number of uncertainties discussed in this review, however, it is by no means certain that the Kf actually does play this central role in the physiological regulation of glomerular function.
Role of atrial peptide in the natriuresis and diuresis that follows relief of obstruction in rat
Authors: Purkerson M. L. , Blaine E. H. , Stokes T. J. , Klahr S.
Published: December 2017

The present studies demonstrate that endogenous levels of atrial peptide are significantly elevated in the plasma of rats with bilateral ureteral obstruction (BUO) compared with control rats or rats with unilateral ureteral obstruction. The contribution of endogenous atrial peptide to the natriuresis and diuresis that follows release of BUO was examined by the intravenous infusion of heparin with or without the exogenous administration of atrial peptide. Infusion of heparin, which binds atrial peptide and interferes with its biological effect, decreased the natriuresis and diuresis observed after release of BUO. Heparin administration also markedly blunted the natriuresis and diuresis observed after exogenous administration of atrial peptide following release of BUO in rats. In contrast, heparin administration did not decrease the natriuresis and diuresis seen in the experimental kidney after relief of unilateral ureteral obstruction. The finding of increased plasma levels of atrial peptide in rats with bilateral ureteral obstruction together with the decrease in diuresis and natriuresis observed with the administration of heparin after release of BUO in these animals indicate that endogenous levels of atrial peptide contribute to the natriuresis and diuresis that occur after release of BUO in rats.
Angiotensinogen's role in ANG formation, renin release, and renal hemodynamics in isolated perfused kidney
Authors: Misumi J. , Gardes J. , Gonzalez M. F. , Corvol P. , Menard J.
Published: December 2017

Isolated perfused rat kidneys were used to investigate the effects of the addition of pure angiotensinogen or renin-free plasma to the perfusate on angiotensin I (ANG I) and angiotensin II (ANG II) generation, renal hemodynamics, and renin release. When no angiotensinogen or plasma is added, a very small amount of angiotensinogen is initially detected in the perfusate. Whereas renin secreted by the kidney accumulates in the perfusate, angiotensinogen disappears during the perfusion and immunoreactive ANG II cannot be detected. The addition of angiotensinogen reactivates the renin-angiotensin system. ANG I, [des-Asp1] ANG I, ANG II, and [des-Asp1] ANG II are progressively generated in the perfusate. At a constant perfusion pressure, as well as at a variable perfusion pressure, a progressive fall in renal perfusate flow is observed that is significantly correlated to the level of immunoreactive ANG II. ANG II significantly blunts the rise in renin, and renin release in the perfusate is negatively correlated to immunoreactive ANG II levels. Comparison of the ANG I and ANG II levels in in vitro incubated perfusates and circulated perfusates shows that in plasma-injected perfusates the level of immunoreactive ANG II is dependent on both the production of ANG I and its conversion to ANG II by renal and perfusate converting-enzyme activity, and on ANG I and ANG II degradation by the kidney and the perfusate.
Glomerular dynamics and salt balance in pregnant rats with renal hypertension
Authors: Dal Canton A. , Altomonte M. , Conte G. , Esposito C. , Fuiano G. , Romano G. , Russo D. , Sabbatini M. , Uccello F. , Veniero P. , et al.
Published: December 2017

These studies were aimed at investigating whether chronic hypertension in pregnancy causes changes both in salt excretion (NaE) and in glomerular hemodynamics. Metabolic and renal micropuncture studies were performed in pregnant (P) and Virgin (V) Munich-Wistar rats with normal blood pressure (N) and two-kidney Goldblatt hypertension (H). Mean NaE was higher in PN than VN (2.7 vs. 1.7 meq/day, P less than 0.01). Hypertension raised NaE both in P and V rats: in P and V rats with "benign" hypertension (blood pressure less than 180 mmHg) NaE averaged 3.2 and 2.6 meq/day, respectively (P less than 0.05); mean NaE was 5.9 and 3.8 meq/day, respectively (P less than 0.01), in P and V rats with "malignant" hypertension (blood pressure greater than or equal to 180 mmHg). Afferent arteriole resistance (Ra) averaged 1.73 and 3.50 10 dyn.s-1.cm5 in PN and VN, respectively (P less than 0.01). Hypertension raised Ra in V, but not in P rats (4.47 vs. 2.14 10 dyn.s-1.cm5, P less than 0.01). Thus glomerular plasma flow, glomerular capillary hydrostatic pressure, and single-nephron glomerular filtration rate were markedly higher in PH than VH rats: in PH rats single-nephron filtration fraction was significantly lower than in VH. These results show that in PH rats a marked rise in NaE is associated with glomerular vasodilation.
Regulation of plasminogen activation in isolated perfused rat kidney
Authors: Muellbacher W. , Maier M. , Binder B. R.
Published: December 2017

To better understand the mechanism and regulation of plasminogen activation within the kidney, the release and excretion of plasminogen activator activities was studied in the isolated perfused rat kidney in the absence and presence of plasminogen substrate. In the absence of plasminogen, the kidneys released a constant amount of plasminogen activator activity into both the urine and the perfusate. On continuous infusion of purified human plasminogen into the perfusate, the release of plasminogen activator activity into the urine slightly increased, and plasmin generated could be detected in both urine and perfusate. With the use of specific antibodies against the tissue-type (t-PA) and the urokinase-type plasminogen activator (u-PA), respectively, the activity in the perfusate could be identified as t-PA, whereas the activity in the urine could be ascribed to u-PA. A bolus injection of either antibody into the plasminogen-supplemented perfusion medium completely inhibited plasminogen activator activity and generation of plasmin in the vascular or tubular compartment. Furthermore, intrarenal inhibition of t-PA activity by the specific antibody significantly increased the concentration of plasminogen in the perfusate, indicating decreased consumption. This effect was accompanied by increased excretion of u-PA into the urine, suggesting that the availability of intact plasminogen in the renal circulation directly or indirectly might participate in the regulation of u-PA excretion into the urine.
A structural study of the rat proximal and distal nephron: effect of peptide and thyroid hormones
Authors: Koechlin N. , Elalouf J. M. , Kaissling B. , Roinel N. , de Rouffignac C.
Published: December 2017

The effects of the absence of various hormones (antidiuretic hormone, thyroid hormone, parathyroid hormone, and calcitonin) on proximal and distal structures were studied in diabetes insipidus (DI) Brattleboro rats. The cross-sectional area of the first segment of proximal convoluted tubules (Sl) was significantly reduced in thyroparathyroidectomized (TPTX) DI rats compared with Long-Evans rats (the strain of origin of DI rats) and untreated DI rats. Administration of triiodothyronine (T3, 10 μg/day for 7 days) to TPTX-DI rats restored the proximal tubule structure. In the distal convoluted tubule (DCT) the cross-sectional area of the epithelium and the number of nuclei per cross-sectional area were significantly greater in untreated ADH-deficient DI rats than in the control Long-Evans rats. Daily administration of 1-desamino-8-d-arginine vasopressin (dDAVP, 500 ng/day for 3 wk) significantly reduced the size and the number of DCT cells in DI rats. Cortical micropuncture data indicated that the Na+ concentration in the fluid delivered to the DCT and the absolute amount of Na+ reabsorbed along the DCT were higher in DI than in dDAVP-treated DI rats. It is concluded that functional changes in the PCT, subsequent to chronic TPTX, are accompanied by marked alteration of the cell anatomy of this nephron segment, and that the processes that modify the Na load delivered to the DCT and the Na transport in the DCT are accompanied by structural modifications of this segment.

Brattleboro rat; antidiuretic hormone; triiodothyronine; morphology of distal convoluted tubule cells; long-term treatment with antidiuretic hormone; sodium transport by the distal convoluted tubule; micropuncture study

Submitted on January 12, 1988

Accepted on December 15, 1988
Active urea transport in toad skin is coupled to H+ gradients
Authors: Rapoport J. , Chaimovitz C. , Hays R. M.
Published: December 2017

Active transport of urea exists inwardly through the skin of the toad Bufo viridis and is enhanced by adapting the toads to hypertonic saline solutions. In this paper, we report our studies on the energy coupling of this active transport system. We have shown previously that this system is independent of sodium transport. We thus studied the possibility of coupling to proton transport by studying the following: 1) the effect of acidifying the epithelium by means of CO2 and protonophores, 2) the effect of alkalinizing the epithelium with the anion-exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and by removal of chloride from the serosal medium, 3) the effect of inhibiting the proton-translocating ATPase of the skin, 4) dependence on mucosal pH. We found that 1) acidification of the epithelium by means of 5% CO2 and the protonophores carbonyl cyanide m-chlorophenylhydrazone (CCCP) and nigericin inhibited urea influx; 2) alkalinization of the epithelium by means of the disulfonic stilbene DIDS and by removal of serosal chloride increased urea influx; 3) inhibition of the proton-translocating ATPase of the skin by means of 1,3-dicyclohexylcarbodiimide (DCCD), N-ethylmaleimide (NEM), and sodium orthovanadate inhibited urea transport; 4) urea influx was unaffected by alkalinizing the external medium to 8.5 or by acidifying to 6.5; it was significantly suppressed by a mucosal pH of 5.5.(ABSTRACT TRUNCATED AT 250 WORDS)
Use of fluorescent dye BCECF to measure intracellular pH in cortical collecting tubule
Authors: Weiner I. D. , Hamm L. L.
Published: December 2017

The compound 2'-7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) is being extensively used to measure intracellular pH (pHi) in a variety of tissue preparations. Use of this dye in the isolated perfused rabbit cortical collecting tubule (CCT) revealed two previously unreported findings. Apical incubation via luminal perfusion with the acetoxymethyl ester of BCECF (BCECF-AM) resulted in intense uptake into a minority cell population. Basolateral incubation via the peritubular bathing solution resulted in apparent homogenous uptake into all cells. The minority cells were identified as intercalated cells by the use of fluorescent probes specific for intercalated cells. Minority cell pHi was 7.34 +/- 0.06 (n = 9); majority cell pHi was 7.41 +/- 0.05 (n = 6). In addition, prolonged excitation of BCECF resulted in adverse effects. Intense continuous excitation for 1-3 min resulted in a fall in apparent pHi of 0.53 +/- 0.05 pH units (n = 6, P less than 0.001). After reloading with fresh BCECF-AM, the calculated pHi was 0.05 +/- 0.07 pH units higher than before prolonged excitation (P = NS), suggesting that the apparent decrease was due to changes in the pH sensitivity of BCECF as a result of the prolonged excitation. Prolonged excitation of cells with pHi clamped at 7.50 resulted in a decline in apparent pHi at the rate of 0.15 +/- 0.02 pH units/min (n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)
Proton compartmentation in rat renal cortical tubules
Authors: Schoolwerth A. C. , Gesek F. A. , Culpepper R. M.
Published: December 2017

To study the control of renal ammoniagenesis, a technique was developed to estimate simultaneously intracellular (pHi) and intramitochondrial (pHm) pH in suspensions of rat renal cortical tubules. pHi was estimated with the fluorescent probe 2',7'biscarboxyethyl-5(6)-carboxy-fluorescein (BCECF). The intracellular distribution of the weak acid 5,5-dimethyloxazolidine-2,4-dione (DMO) allowed calculation of pHm with the use of values of pHi obtained with BCECF and tubule mitochondrial content. At medium pH (pHe) 7.4, pHi was 7.08 +/- 0.02. Over the pHe range 7.0-7.7, pHi was linearly related to pHe, but the pH gradient across the cell membrane decreased as pHe was lowered. No difference in the relationship between pHe and pHi was obtained when tubules were incubated in the presence of a nonbicarbonate or bicarbonate-buffered medium. Changes in pHe with bicarbonate-buffered media resulted in identical pHi values, whether the changes were induced by altered bicarbonate or CO2 content. At pHe 7.4, pHm was 7.78 +/- 0.6 in bicarbonate-buffered medium but was higher (0.2-0.3 pH units) when tubules were bathed in nonbicarbonate-buffered medium. pHm was linearly related to pHi in either buffer. The pH gradient across the inner mitochondrial membrane was also positively correlated with pHe. The present studies indicate the suitability of the techniques for estimating pHi and pHm simultaneously in suspensions of rat renal cortical tubules. Parallel changes occur in both intracellular compartments when pHe is altered. pHm, which is approximately 0.7 pH units greater than pHi, decreases in acute acidosis. This decrease may be important in stimulating renal ammoniagenesis, possibly by activation of alpha-ketoglutarate dehydrogenase.
Regulation of renal ion transport and cell growth by sodium
Authors: Stanton B. A. , Kaissling B.
Published: December 2017

Intracellular sodium has been implicated in a variety of cellular processes including regulation of Na+-K+-ATPase activity, mitogen-induced cell growth, and proliferation and stimulation of Na+-K+-ATPase by aldosterone. In renal epithelial cells a rise in sodium uptake across the apical membrane increases intracellular sodium concentration, which in turn stimulates the turnover rate of Na+-K+-ATPase and thereby enhances sodium efflux across the basolateral membrane. A prolonged increase in sodium uptake causes dramatic hypertrophy and hyperplasia and a rise in the quantity of Na+-K+-ATPase in the basolateral membrane. These structural and functional changes occur in the kidney in the absence of alterations in plasma aldosterone and vasopressin levels. Several mitogens induce growth and proliferation by initiating a cascade of events, which include a rise in intracellular sodium. Accordingly, an increase in the sodium concentration within renal epithelial cells may elicit a “mitogen-like” effect by initiating the cascade at the sodium step, even in the absence of a mitogen. A rise in cell sodium may also stimulate the production of autocrine growth factors that directly or indirectly regulate cell growth and proliferation, by modifying the response to mitogens or to changes in the ionic composition of the extracellular fluid. In this review we will examine the evidence that supports a role for intracellular sodium in regulating these cellular events in renal epithelial cells.