bluuebunny/crossref_metadata_2025 huggingface dataset:
Ammonia transport by the turtle urinary bladder
Authors: Arruda J. A. , Dytko G. , Withers L.
Published: December 2017

Ammonia transport across the turtle bladder was examined by adding NH4Cl to the serosal (S) or mucosal (M) solution. With appropriately fixed levels of pH and/or NH4Cl concentration the transepithelial flow of ammonia parallels the extracellular concentration of NH+4 while that of NH3 is kept constant and parallels the extracellular concentration of NH3 while that of NH+4 is kept constant. This suggests that NH+4 as well as NH3 traverses the bladder wall. The apparent S----M permeability to NH3 was 15-18 times greater than that to NH+4. At pH 6.4 in both S and M solutions, the net flow of ammonia was from S----M, but at pH 8.4 in the S and 6.4 in the M or vice versa ammonia transport was of the same magnitude in both directions. The relative permeability of the M membrane to NH+4 was less than that to Na and nearly the same as that to K. The relative permeability of the S membrane to NH+4 was greater than that to K. At S pH of 8.4 and M pH of 6.4, ammonia transport was a linear function of NH4Cl concentration. At S pH of 6.4 and M pH of 6.4, ammonia transport was a saturation function of NH4Cl concentration in that it was linear up to 5 mM and constant and maximal in excess of 7.5 mM. The net transport of methylamine directed from S to M was competitively inhibited by NH4Cl, suggesting that the two substances are transported through a common carrier system. At pH 6.4 in both S and M, the S addition of NH4Cl induced an increase in reverse short-circuit current, the magnitude of which approximated the chemically determined rate of ammonia transport. This means that ammonia transport at pH 6.4 is, at least in part, electrogenic due to the flow of ionic NH+4 through a transbladder conductive path. However, when the S pH was raised to 8.4 the increase in ammonia transport was not associated with an increase in current. The present study demonstrates that the turtle bladder is capable of transporting ammonia with different characteristics of NH+4 and NH3 transport.
Steroid regulation of Na+-K+-ATPase: differential sensitivities along the nephron
Authors: Rayson B. M. , Lowther S. O.
Published: December 2017

Steroid hormonal activation of the Na+-K+-ATPase enzyme was examined in enriched preparations of outer medullary collecting tubules (MCT) and outer medullary thick ascending limbs of the loop of Henle (MAL), prepared by sedimentation through a discontinuous Ficoll gradient. Using morphological criteria, there was a 2.9-fold enrichment of MCT in fraction 1 when compared with fraction 2 and a 2.2-fold enrichment of MAL in fraction 2 when compared with fraction 1. This separation was further defined using biochemical markers. Na+-K+-ATPase activity, Mg2+-ATPase activity, and the adenylate cyclase response to a number of hormones each supported the morphologic definition of separation. The two preparations were challenged in vitro with both aldosterone and dexamethasone. In fraction 1, the fraction enriched in the MCT, 10(-8) M aldosterone stimulated Na+-K+-ATPase activity by 37%. The same concentration of dexamethasone was without effect. In contrast, 10(-8) M dexamethasone stimulated Na+-K+-ATPase activity by 27% in fraction 2, the fraction enriched in the MAL. In this fraction an equimolar concentration of aldosterone was without effect. Thus, the regulation of Na+-K+-ATPase activity by mineralocorticoids on the one hand and by glucocorticoids on the other would appear to be discontinuously localized along the length of the outer medullary distal nephron.
Circulating epinephrine stimulates renin secretion in anesthetized dogs by activation of extrarenal adrenoceptors
Authors: Johnson M. D.
Published: December 2017

The present experiments were designed to determine the location of the adrenoceptors responsible for initiating epinephrine-induced stimulation of renin secretion in vivo. Three hypotheses were tested: 1) the receptors are located intrarenally, 2) the receptors are located extrarenally , and 3) an interaction exists between intrarenal receptors and some event initiated by extrarenal receptors. All experiments were conducted in anesthetized dogs surgically prepared for renal clearance studies. Intravenous infusion of epinephrine at 250 ng X kg-1 X min-1 increased one-kidney renin secretion rate more than fivefold. In contrast, direct intrarenal infusion of epinephrine at 25 ng X kg-1 X min-1 only doubled renin secretion rate from the infused kidney. In six animals in which renin secretion rates were measured bilaterally during intrarenal epinephrine infusion, no differences in renin secretion rates were detected between the two kidneys. To examine the hypothesis that an interaction exists between intrarenal and extrarenal adrenoceptors, epinephrine was infused intravenously at 25 ng X kg-1 X min-1 and simultaneously into one renal artery at 10 ng X kg-1 X min-1. Renin secretion rates rose significantly (P less than 0.01) but equally from both kidneys. At lower epinephrine infusion rates (10 ng X kg-1 X min-1 intravenously plus 3 ng X kg-1 X min-1 intrarenally), renin secretion rates increased submaximally but still equally from both kidneys. It is concluded that epinephrine-induced stimulation of renin secretion in vivo is initiated by adrenoceptors located only extrarenally .
Na+/H+ antiporter in membrane populations resolved from a renal brush border vesicle preparation
Authors: Mircheff A. K. , Ives H. E. , Yee V. J. , Warnock D. G.
Published: December 2017

A conventional brush border membrane preparation, obtained by divalent cation precipitation of homogenates of rabbit renal cortex, was analyzed by countercurrent distribution in an aqueous dextran:polyethylene glycol two-phase system. The resulting fractions were assayed for the presence of the Na+/H+ antiporter and for a variety of biochemical marker enzymes. This analysis revealed four physically distinct membrane populations (A-D). Population A consisted of two subpopulations, A' and A", which were enriched an average of 49-fold in maltase; they were also highly enriched in alkaline phosphatase, leucine aminopeptidase, and Na+/H+ antiporter. On the basis of their marker contents, populations A' and A" appear to represent highly purified, functional brush border membrane vesicles. Population B was enriched twofold in NADPH-cytochrome c reductase and population C was enriched 12-fold in galactosyltransferase. Populations B and C accounted for 25% of the protein in the starting material and appear to reflect contamination of the brush border membrane preparation by subpopulations of endoplasmic reticulum and Golgi fragments. Population D was enriched in Na+/H+ antiporter, alkaline phosphatase, leucine aminopeptidase, Na-K-ATPase, and acid phosphatase but not maltase, NADPH-cytochrome c reductase, galactosyltransferase, or succinate dehydrogenase. Its identity is unclear, and it might consist of a multiplicity of populations from different origins.
Renal effects of overhydration during vasopressin infusion in conscious dogs
Authors: Bie P. , Munksdorf M. , Warberg J.
Published: December 2017

The antidiuretic and possibly natriuretic effects of small doses of vasopressin (AVP) were investigated in conscious dogs. Plasma composition and renal excretion of water, Na+, and K+ were measured after overhydration by 20 ml/kg performed during infusion of AVP at rates of 50, 100, 150, 200, or 400 pg X min-1 X kg body wt-1 or of 1-desamino-8-D-arginine vasopressin (DDAVP) 50 pg X min-1 X kg body wt-1. Hydration lowered plasma osmolality and sodium concentration by 4.2 +/- 0.3 and 3.8 +/- 0.2%, respectively; plasma protein showed a larger decrease, 8.5 +/- 0.4% (P less than 0.01). Urine osmolality during hydration was 52 +/- 3 mosmol/kg H2O. AVP infusion at 100 pg X min-1 X kg-1 elevated plasma vasopressin by 1.7 +/- 0.3 pg/ml and urine osmolality by 1,049 +/- 152 mosmol/kg H2O and elicited marked natriuresis and kaliuresis but no change in osmolar clearance. During DDAVP infusion urine osmolality was 1,365 +/- 134 mosmol/kg H2O, but electrolyte excretion was indistinguishable from control. It is concluded that 1) AVP is associated with marked natriuresis and kaliuresis even in doses required to prevent water diuresis, 2) DDAVP--although strongly antidiuretic--does not affect electrolyte excretion, and 3) the water load causes disproportionate dilution of plasma protein and osmolality, probably due to protein redistribution.
Albumin homeostasis in the nephrotic rat: nutritional considerations
Authors: Kaysen G. A. , Kirkpatrick W. G. , Couser W. G.
Published: December 2017

Albumin catabolism and the relationship between plasma albumin concentration and albuminuria were studied in male Sprague-Dawley rats with Heymann nephritis. The rats were placed on isocaloric diets of 8.5, 21, or 40% protein. Serum albumin concentration correlated negatively with urinary albumin excretion for each of these dietary groups, but the correlation was dependent on dietary protein intake. The magnitude of albuminuria reflected the increase in albumin synthesis rate plus the decrease in albumin catabolic rate. Maximal urinary albumin loss was dependent on dietary protein intake. Albumin catabolism was studied in the different groups of nephrotic animals. Albumin catabolism correlated inversely with the rate of albuminuria in the 21 and 40% protein-fed rats and contributed nearly half of the albumin that was lost in these groups of animals. Albumin catabolism was independent of albuminuria in the rats fed 8.5% protein. The rats were fed 18% of their normal caloric intake, and albumin catabolism was studied in nephrotic and control animals. Albumin catabolism increased with increased albuminuria, in contrast to the well-nourished group, and there was no relationship between serum albumin concentration and urinary albumin excretion. Increased catabolism of albumin plays little or no role in albumin homeostasis in the well-nourished nephrotic rat but may be significant in protein- and calorie-malnourished animals.
Effect of luminal pH and HCO3- on phosphate reabsorption in the rabbit proximal convoluted tubule
Authors: Hamm L. L. , Kokko J. P. , Jacobson H. R.
Published: December 2017

Luminal pH in the proximal convoluted tubule may alter phosphate reabsorption in a variety of acid-base disturbances and in normal conditions as luminal pH decreases along the length of the proximal tubule. These studies address the influence of luminal pH on phosphate reabsorption in isolated perfused proximal convoluted tubules from normal rabbits. Initial perfusates were either pH 6.2 or 7.4, and the bath pH was 7.4. All solutions contained 10 mM total phosphate. The first experiments used HCO3-/CO2-free solutions to examine the effect of luminal pH independent of changes in [HCO3-] or Pco2. Lumen-to-bath phosphate flux increased from 0.63 +/- 0.23 with alkaline perfusate to 2.04 +/- 0.35 pmol X mm-1 X min-1 with acid perfusate. In a separate group of tubules, acetazolamide had no qualitative effect on this result. With HCO3-/CO2-containing solutions, phosphate reabsorption increased from 4.53 +/- 1.46 with alkaline perfusate to 9.67 +/- 1.77 pmol X mm-1 X min-1 with acid perfusate. Thus, an acid luminal fluid can enhance proximal phosphate reabsorption independent of the presence or absence of HCO3-/CO2. To examine the specificity of this effect, the influence of luminal pH on another solute (glucose), reabsorbed via a Na+-coupled mechanism, was studied. Lumen-to-bath glucose flux increased in the same direction: from 52.78 +/- 4.91 with alkaline perfusate to 57.13 +/- 4.70 pmol X mm-1 X min-1 with acid perfusate. The mechanism of the influence of luminal pH on phosphate and glucose reabsorption is not explained but could be direct or indirect from changes in intracellular pH, Na+ activity, metabolism, or basolateral transport. Since an acid luminal pH is expected to inhibit or decrease Na+-H+ exchange at the luminal membrane, these results are also consistent with a competition for the available Na+ gradient between phosphate and glucose transport and the Na+-H+ exchanger in the proximal tubule.
Renal afferent and efferent arterioles of the rabbit
Authors: Gattone V. H. , Luft F. C. , Evan A. P.
Published: December 2017

The present study employed our microdissection-digestion technique to determine the three dimensional organization of the walls of the afferent and efferent arterioles of the adult rabbit kidney. Each smooth muscle cell of an afferent arteriole is characterized by a somal enlargement and two lateral processes. The cells of the distal segment of the afferent arterioles are modified into myoepithelioid cells, which are closely apposed to one another. The cells of the proximal efferent arteriole are irregularly shaped and regions of adjacent cells may be separated from one another so that gaps exist and areas of the underlying endothelium are not covered by smooth muscle cells. The cells of the distal segments of efferent arterioles are multipolar pericytes, of which the processes branch. Thus the afferent arteriole possesses a complete muscular wall while only the proximal efferent possesses smooth muscle cells with a sphincteric orientation. The distal efferent arteriole possesses pericytes that appear to have a limited capability to modulate renal hemodynamics.
Tubuloglomerular feedback and SNGFR autoregulation in the rat
Authors: Moore L. C.
Published: December 2017

Experimental and simulation studies were undertaken to examine what influence the state of filtration dynamics has on single nephron glomerular filtration rate (SNGFR) autoregulation, to verify the presence of partial autoregulation during tubuloglomerular feedback (TGF) inhibition, and to determine whether small changes in tubular reabsorption could enhance the ability of TGF to regulate SNGFR during autoregulation. The experimental studies in hydropenic rats revealed partial autoregulation of glomerular capillary pressure (using the stop-flow method) and SNGFR during TGF inhibition and complete SNGFR autoregulation with functional TGF. A small significant decrease in fractional volume reabsorption was observed in the distal measurements with increased arterial pressure. Results from a mathematical model of glomerular filtration suggest that SNGFR is inherently more sensitive to changes in arterial pressure in animals exhibiting filtration pressure equilibrium rather than filtration pressure disequilibrium. These data and the simulation results provide additional support for the existence of a TGF-independent autoregulatory mechanism that appears to be an intrinsic property of the preglomerular vasculature. Finally, analysis of autoregulation with a simple control-system model suggests that small changes in proximal tubule or loop of Henle volume reabsorption can provide some or all of the stimulus for TGF activation, thereby significantly increasing the ability of TGF to stabilize SNGFR in response to a rise in arterial pressure.
Single-channel currents in renal tubules
Authors: Koeppen B. M. , Beyenbach K. W. , Helman S. I.
Published: December 2017

Patch-clamp techniques were used to study isolated renal cortical collecting ducts of rabbits. Gigaohm seals of the native apical membranes of the principal cells were obtained from tissues superfused with a Ringer solution. No enzymatic or other pretreatment of the tissues was required. The patches studied were primarily of the on-cell type, although excised patches could be obtained. Unitary currents in a range of tenths of picoamperes were observed at holding voltages between +/- 100 mV. Since the apparent reversal potential was at a holding voltage at or near 0 eatment of the tissues was required. The patches studied were primarily of the on-cell type, although excised patches could be obtained. Unitary currents in a range of tenths of picoamperes were observed at holding voltages between +/- 100 mV. Since the apparent reversal potential was at a holding voltage at or near 0 eatment of the tissues was required. The patches studied were primarily of the on-cell type, although excised patches could be obtained. Unitary currents in a range of tenths of picoamperes were observed at holding voltages between +/- 100 mV. Since the apparent reversal potential was at a holding voltage at or near 0 mV and since the current-voltage relationship was markedly nonlinear, the unitary currents are most likely due to K+ . Na+-channel current fluctuations, if present, could not be uniquely identified in the presence or absence of amiloride.
Dopamine receptors in the proximal tubule of the rabbit
Authors: Felder R. A. , Blecher M. , Calcagno P. L. , Jose P. A.
Published: December 2017

Our laboratory has characterized dopamine receptors in glomeruli and tubular homogenates. Since the heterogeneity of kidney homogenates limits the interpretation of these studies, the [3H]haloperidol binding site and adenylate cyclase sensitivity to dopamine were studied in the isolated proximal convoluted tubule and pars recta of the rabbit kidney. [3H]Haloperidol binding sites were saturable, stereoselective, and of high affinity. The apparent dissociation constant was 31.5 X 10(-9) M (+/- 8.5) and the maximum receptor density was 0.31 X 10(-15) M (+/- 0.08) per millimeter. In pars recta specific binding was 53% of total [3H]-haloperidol binding. Dopamine stimulated adenylate cyclase activity in a dose-related manner, which was inhibited by cis-flupenthixol but not by trans-flupenthixol or (-)-propranolol. Moreover, the stimulatory effect of the dopamine 1 (D1) agonist SKF 82526 on adenylate cyclase activity was blocked by the D1 antagonist SCH 23390. Dopamine receptors in the proximal convoluted tubule appear to be of the D1 subtype since they are linked to stimulation of adenylate cyclase. This is further substantiated by the stereoselectivity for (+)-sulpiride (a D1 antagonist), which had a greater affinity for the [3H]haloperidol binding site than (-)-sulpiride (a D2 antagonist).
Effects of synthetic atrial natriuretic factor on renal function and renin release
Authors: Burnett J. C. , Granger J. P. , Opgenorth T. J.
Published: December 2017

Studies were performed in anesthetized dogs (n = 5) to determine the effects of synthetic atrial natriuretic factor on renal function and renin release. Intrarenal infusion of synthetic atrial natriuretic factor (ANF) (0.3 microgram X kg-1 X min-1) resulted in a transient increase in renal blood flow (126 +/- 8 to 148 +/- 11 ml/min). The duration of this transient vasodilation was 3.1 +/- 0.4 min. Continued infusion was followed by a slight decrease in renal blood flow (126 +/- 8 to 117 +/- 8 ml/min) and an increase in glomerular filtration rate (23.1 +/- 3.5 to 30.7 +/- 1.9 ml/min), with filtration fraction thus being increased (0.19 +/- 0.04 to 0.27 +/- 0.03). These hemodynamic alterations were associated with increases in fractional sodium excretion (0.6 +/- 0.2 to 5.8 +/- 0.8%), fractional potassium excretion (30.8 +/- 9.4 to 56.3 +/- 7.4%), fractional lithium excretion (32.2 +/- 7.1 to 60.3 +/- 5.7%), and fractional phosphate excretion (8.7 +/- 3.5 to 41.6 +/- 11.7%). Intrarenal infusion of synthetic ANF markedly suppressed renin secretion rate (295.5 +/- 84.6 to 17.2 +/- 10.6 ng/min) despite a slight reduction in arterial pressure (123 +/- 9 to 118 +/- 9 mmHg). Our studies demonstrate that synthetic ANF results in a marked natriuretic response that is in part mediated by an increase in glomerular filtration rate. The increase in fractional lithium and phosphate excretion suggests that this factor may also have an action on proximal tubule reabsorption. Further, these studies demonstrate that synthetic ANF markedly inhibits renin secretion.
Effects of bradykinin on renal interstitial pressures and proximal tubule reabsorption
Authors: Mertz J. I. , Haas J. A. , Berndt T. J. , Burnett J. C. , Knox F. G.
Published: December 2017

Contents: the correct title for the article on page F82 by J. I. Mertz, J. A. Haas, T. J. Berndt, J. C. Burnett, Jr., and F. G. Knox is “Effects of bradykinin on renal interstitial pressures and proximal tubule reabsorption.”
Effect of aluminum on the renal handling of phosphate in the rat
Authors: Burnatowska-Hledin M. , Klein A. M. , Mayor G. H.
Published: December 2017

The effects of aluminum (Al) on the renal handling of phosphate (Pi) were studied by clearance techniques in the presence and absence of endogenous parathyroid hormone (PTH) and after Pi infusion. In all groups, a 1-h control period was followed by three 1-h experimental periods in which controls continued to receive saline and experimental animals received Al. Glomerular filtration rate, urine flow rate, and plasma sodium (Na) were not significantly changed between periods in any group. In the presence of endogenous PTH, the fractional excretion of phosphate (FEPi) increased significantly after 3 h of Al infusion (6.1 +/- 0.9 to 15.0 +/- 1.8%, P less than 0.05, n = 8), but not in controls (n = 7), while plasma calcium and Pi decreased, suggesting a PTH effect. However, in acutely thyroparathyroidectomized (TPTX) rats the FEPi also increased significantly after 3 h of Al infusion (4.3 +/- 3.0 to 10.6 +/- 4.2%, P less than 0.05, n = 7), but not in controls (n = 6). In TPTX rats infused with Pi where plasma Pi was increased to 10 mg/dl, FEPi increased significantly after 2 and 3 h of Al (7.0 +/- 1.4 to 15.5 +/- 2.1 to 16.9 +/- 2.2%, P less than 0.01, n = 15), but not in controls (n = 8). In this group, changes in FEPi were accompanied by a small but significant increase in FENa but not urinary cAMP. Blood pH was not significantly different between saline and Al-infused rats. These studies indicate that Al infusion inhibits renal Pi reabsorption by a mechanism independent of PTH, blood pH, or cAMP.
Plasma volume expansion is necessary for edema formation in the rate with Heymann nephritis
Authors: Kaysen G. A. , Paukert T. T. , Menke D. J. , Couser W. G. , Humphreys M. H.
Published: December 2017

Edema formation in nephrotic syndrome has been attributed to intravascular volume depletion resulting from leakage of plasma water into the interstitial space and activating secondary renal sodium retention. However, clinical studies indicate that edematous patients with nephrotic syndrome may have normal or expanded plasma volumes. We evaluated the relationship between plasma volume and edema formation in control rats and rats with chronic renal failure (CRF) produced by 7/8 nephrectomy. In each group, plasma volume and 22Na space were measured during the control period and after induction of hypoalbuminemia from passive Heymann nephritis. Rats with CRF had expanded plasma volume during the initial period (4.23 +/- 0.46 vs. 3.32 +/- 0.68 ml/100 g body wt) that became significantly more expanded (to 5.44 +/- 1.16 ml/100 g body wt) when they became nephrotic as 22Na space also increased. Plasma volume and 22Na space did not change in the sham-operated rats when nephrosis was produced. Plasma renin activity was lower in the CRF rats during the control period than in the sham-operated rats and fell significantly during the nephrotic period when edema developed. Nonnephrotic rats had a plasma colloid osmotic pressure (COP) of 17.8 +/- 4.3 mmHg compared with 8.5 +/- 2.9 mmHg when nephrotic. Despite this large difference in COP, both nephrotic and nonnephrotic rats exhibited the same relationship between plasma volume and extravascular sodium space, a measure of edema formation. Hypoproteinemia is not sufficient for edema formation in the rat with passive Heymann nephritis; concomitant plasma volume expansion resulting from CRF is a necessary additional component.
A distributed model of peritoneal-plasma transport: tissue concentration gradients
Authors: Flessner M. F. , Fenstermacher J. D. , Dedrick R. L. , Blasberg R. G.
Published: December 2017

Peritoneal dialysis transport studies were carried out in anesthetized rats. Injections of [14C]EDTA were made by intravenous bolus or intraperitoneal dialysis solution, and blood and peritoneal fluid samples were collected for 1 h. After death and rapid freezing of the animal, transverse sections through the abdominal cavity were cut for quantitative macroautoradiography. The plasma-to-peritoneal transport experiments with a clinical dialysis solution resulted in essentially horizontal concentration profiles versus distance in all tissues except large intestine. Estimates of the extracellular tissue fraction were: small intestine, 0.34; large intestine, 0.28; stomach, 0.30; uterus, 0.66; liver 0.35; diaphragm, 0.16; and anterior abdominal wall, 0.15. Similar experiments with an isotonic salt solution resulted in larger (13-300%) extracellular fractions in all tissues. In contrast, peritoneal-to-plasma transport studies demonstrated decreasing concentration profiles in all visceral tissues, with the first 90% of the gradient contained in the initial 400 micron of tissue from the peritoneum. Parietal tissue gradients were less steep and had higher concentration levels deep within the tissue than visceral tissues. Computer simulations using a distributed model approach compared favorably with the experimental measurements and established the validity of this approach.
Effect of potassium depletion on chloride transport in the loop of Henle in the rat
Authors: Luke R. G. , Booker B. B. , Galla J. H.
Published: December 2017

Microperfusion of the superficial loop segment (latest proximal to earliest distal tubule) was performed in potassium-depleted and control rats. Potassium depletion was confirmed by analysis of muscle content (control 45 +/- 2, potassium depletion 33.5 +/- 0.9 meq/100 g dry solids). During perfusion at 20 nl/min net chloride absorption was decreased (66 +/- 3 vs. 77 +/- 2%, P less than 0.01) and early distal chloride concentration increased (70 +/- 5 vs. 50 +/- 4 meq/liter, P less than 0.01) in the potassium-depleted rats. In separate paired experiments in potassium-depleted rats, indomethacin infusion increased net chloride absorption (P less than 0.05) and lowered early distal chloride concentration (P less than 0.05) toward, but not to, normal. A similar effect of indomethacin to decrease early distal chloride concentration was seen in rats ingesting a normal diet and in control rats. We conclude that in potassium-depleted rats there is impaired net chloride absorption in the loop segment, most likely in the thick ascending limb, and that this effect is not produced by an altered response to prostaglandins. This defect in chloride transport may be responsible, at least in part, for the impaired concentrating capacity seen in potassium-depleted rats.
Alpha 2-adrenoceptor antagonism of vasopressin-induced changes in sodium excretion
Authors: Smyth D. D. , Umemura S. , Pettinger W. A.
Published: December 2017

Alpha 2-adrenoceptor agonists attenuate vasopressin-mediated changes in water excretion. The effects on sodium excretion, however, are unclear. We therefore utilized the nonrecirculating isolated perfused rat kidney to study the direct effects of vasopressin and alpha 2-adrenoceptor stimulation on sodium and water excretion in the absence of systemic regulatory systems. The perfusate was a Krebs-Henseleit solution (3.5 g/100 ml Ficoll; 1.0% albumin; 36 degrees C) containing prazosin (30 nM) and propranolol (100 nM) to prevent effects of alpha 1- and beta-adrenoceptor stimulation. Vasopressin (10 microU/ml) produced a significant (P less than 0.05) decrease in both water and sodium excretion. Potassium excretion was not significantly altered. Alpha 2-Adrenoceptor stimulation with l-epinephrine (28 nM) reversed (P less than 0.05) the effects of vasopressin on water and sodium excretion. To confirm that this attenuation was mediated by alpha 2-adrenoceptors, an alpha 2-adrenoceptor antagonist, yohimbine, was administered. Yohimbine (300 nM) blocked the effects of epinephrine on sodium and water excretion (P less than 0.05). The adenosine P-site agonist, SQ 22,536 (100 microM), which mediates its effects through inhibition of adenylate cyclase, produced the same reversal as that of epinephrine on vasopressin-mediated changes. Thus alpha 2-adrenoceptor stimulation antagonized the effects of vasopressin on both water and sodium excretion at the renal level. A corollary to this conclusion is that the function-specific activation of renal adenylate cyclase determines the effect of alpha 2-adrenoceptor stimulation.
ATP-dependent H+ pump in membrane vesicles from rat kidney cortex
Authors: Sabolic I. , Haase W. , Burckhardt G.
Published: December 2017

The presence of membrane vesicles containing an ATP-driven H+ pump was demonstrated in rat kidney cortex homogenate using the delta pH-sensitive dye acridine orange (AO). These vesicles were purified by differential and Percoll density gradient centrifugation. ATP-driven H+ uptake was about 20-fold enriched compared with the homogenate. Determination of marker enzyme activities indicated that these vesicles do not originate from brush border and basolateral membranes, lysosomes, endoplasmic reticulum, mitochondria, Golgi membranes, or red blood cells. The identity with brush border membranes was further excluded by the absence of Na+-H+ exchange. Renal cortical endocytotic vesicles that had taken up horseradish peroxidase or fluorescein isothiocyanate-labeled dextran (FITC-dextran) after injection of these substances into rats in vivo comigrated with the H+ pump activity on the Percoll gradient. Similar characteristics of the H+ pump demonstrated by the AO method and by fluorescence changes of in vivo trapped FITC-dextran proved the identity of H+ pump-containing vesicles with endocytotic vesicles. ATP-driven H+ uptake into endocytotic vesicles was stimulated by Cl- and weakly inhibited by oligomycin. N-ethylmaleimide, dicyclohexylcarbodiimide, and Dio-9 were stronger inhibitors. Histochemical studies revealed that horseradish peroxidase-filled endocytotic vesicles are localized in the apical region of proximal tubule cells. An H+ pump with similar characteristics, but much lower activity, was found in brush border membranes, basolateral membranes, and mitochondria isolated by standard techniques, suggesting a possible contamination of these preparations with endocytotic vesicles.
Atriopeptins: correlation between renal vasodilation and natriuresis
Authors: Wakitani K. , Cole B. R. , Geller D. M. , Currie M. G. , Adams S. P. , Fok K. F. , Needleman P.
Published: December 2017

The effect of atrial peptides on renal function was studied in intact anesthetized dogs. A quantitative comparison of bolus intra-arterial injections demonstrated a rank order potency as renal vasodilators and natriuretic/diuretic agents as follows: ser-leu-arg-arg-atriopeptiin III (SLRR-APIII) greater than high molecular weight artrial peptide greater than or equal to atriopeptin (AP)III = APII much greater than API (essentially inactive). A sustained infusion of APIII was employed in order to study the temporal and quantitative correlation of the renal functional changes induced by the atrial peptide. Both intra-arterial and intravenous administration of the peptide produced concentration-dependent increases in renal blood flow, urine volume, sodium excretion, and osmotic clearance. Infusion of APIII into the renal artery did not alter systemic blood pressure or heart rate. Intravenous infusions of APIII required 10 times higher doses to induce the changes in renal vascular resistance and electrolyte excretion, and a fall in blood pressure and tachycardia resulted. The natriuretic-diuretic effect of the atriopeptins appears to be closely associated with renal vasodilation, exhibiting a positive linear correlation between the peptide-induced changes in sodium excretion and changes in renal blood flow.
pH regulation of endogenous acid production in subjects with chronic ketoacidosis
Authors: Hood V. L.
Published: December 2017

In a previous study of starvation-induced acute ketoacidosis, net ketoacid production was inhibited by acid and facilitated by base ingestion. To determine whether hydrogen ion modifies net ketoacid production during chronic ketoacidosis, six over-weight volunteers ingested NaHCO3, NaCl, or NH4Cl (2 mmol X kg-1 X day-1), each for 7 days, during weeks 6-8 of ketogenic dieting. During days 4-7 of each phase, blood bicarbonate was stable but lower in the NH4Cl (19.6 +/- 0.7 mM) than the NaHCO3 (23.7 +/- 0.7 mM) phases. Throughout these periods, acid intake differed by 216 mmol/day, whereas acid output differed by 129 mmol/day between the NaHCO3 and the NH4Cl phases. The major contribution to this difference in acid balance was a difference in net organic acid (ketoacid) production. Although blood ketones were stable, ketoacid excretion, reflecting net ketoacid production, was decreased by 59% with acid and increased by 66% with base compared with NaCl (control) ingestion. Thus, in this state of chronic ketoacidosis, challenges to acid-base balance were countered by a rapidly occurring, sustained, reversible, and quantitatively significant modification of net acid production which acted as an effective mechanism for acid-base regulation.
Relationship among parathyroid hormone, cAMP, and calcium on proximal tubule sodium transport
Authors: Dolson G. M. , Hise M. K. , Weinman E. J.
Published: December 2017

Parathyroid hormone (PTH), through the generation of cAMP, inhibits the transport of sodium, bicarbonate, and water in the proximal convoluted tubule. The present studies were designed to determine whether the response to PTH or dibutyryl cAMP by proximal renal tubules requires an influx of calcium into the cells or an alteration in the cytosolic concentration of calcium. O2 consumption was determined in an enriched suspension of rabbit proximal convoluted tubules, and the ouabain-sensitive component of O2 consumption was taken as a measure of sodium transport. PTH (1 IU/ml) inhibited the ouabain-sensitive component of O2 consumption from 14.2 +/- 1.6 to 8.9 +/- 1.1 nmol O2 X min-1 X mg protein-1 (P less than 0.005). Dibutyryl cAMP (10(-4) M) inhibited ouabain-sensitive O2 consumption from 12.0 +/- 1.1 to 8.4 +/- 0.8 nmol O2 X min-1 X mg protein-1 (P less than 0.005). In the presence of lanthanum (5-50 microM) or verapamil (20-200 microM), PTH inhibited ouabain-sensitive O2 consumption by 21.3 +/- 3.4% (P less than 0.025) and 33.9 +/- 5.5% (P less than 0.025), respectively. Dibutyryl cAMP inhibited the ouabain-sensitive O2 consumption by 22.6 +/- 7.1% (P less than 0.025) in the presence of lanthanum and 35.4 +/- 3.1% (P less than 0.01) in the presence of verapamil. To more directly assess the cytosolic concentration of calcium, the fluorescent intensity of quin 2-loaded tubules was determined. As compared with timed controls, exposure to PTH resulted in a lower cytosolic concentration of calcium over the 10 min of incubation. Dibutyryl cAMP had a similar effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Renorenal reflexes: neural components of ipsilateral and contralateral renal responses
Authors: Kopp U. C. , Smith L. A. , DiBona G. F.
Published: December 2017

In anesthetized rats, stimulating renal mechanoreceptors (MR) by increasing renal venous pressure (RVP) 22 mmHg increased ipsilateral (ipsi) renal vascular resistance (RVR) from 23.5 to 31.3 mmHg/(ml X min-1 X g-1), ipsi urinary sodium excretion (UNaV) from 0.26 to 0.49 mumol X min-1 X g-1, contralateral (contra) urine flow rate (V) from 3.13 to 4.43 microliter X min-1 X g-1, and UNaV from 0.30 to 0.46 mumol X min-1 X g-1. Ipsi renal denervation (DNX) did not affect the increase in ipsi RVR but reduced the increase in ipsi UNaV. The increases in contra V and UNaV were abolished by either ipsi or contra renal DNX. Increases RVP increased ipsi afferent renal nerve activity (ARNA) 288 counts/10 s and decreased ipsi and contra efferent renal nerve activity (ERNA) 242 and 490 counts/10 s, respectively. Renal pelvic instillation of lidocaine (5 micrograms/ml) did not affect the renal functional or electrophysiological responses to increases RVP but abolished the increase in ipsi ARNA, the decrease in contra ERNA, and the increases in contra V and UNaV produced by increasing ureteral pressure (UP) or retrograde ureteropelvic perfusion with 0.9 M NaCl [chemoreceptor (CR) stimulation]. Chronic T6 spinal cord section abolished the increase in ipsi ARNA, the decrease in contra ERNA, and the increases in contra V and UNaV produced by renal MR (increases RVP, increases UP) and CR stimulation. We conclude increases that RVP results in an ipsi and contra inhibitory renorenal reflex. Differential blockade with pelvic lidocaine suggests that the sensory receptors activated by increases RVP are located in an anatomically different area than those activated by increases UP or retrograde ureteropelvic perfusion with 0.9 M NaCl. An intact spinal cord is required for the normal responsiveness of renal sensory neuroreceptor complexes to specific stimuli in the context of the complete renorenal reflex response.
Identification of the bicarbonate secretory cell of the turtle bladder
Authors: Fritsche C. , Schwartz J. H.
Published: December 2017

The turtle bladder consists primarily of two mucosal cell types, mitochondrial rich (MR) and granular (G) cells. The MR cells secrete H+. In addition, the bladder secretes HCO3-, an energy-requiring Cl(-)-dependent transport system. These studies were designed to identify the cell type responsible for HCO3- secretion. Specific HCO3- and H+ secretory inhibitors were added to alter O2 consumption of MR and G cells. Cells were separated by Ficoll density centrifugation. Ouabain (10(-4) M) was used in all studies to eliminate O2 consumption associated with Na+ transport. O2 consumption of cells treated with 10(-4) M 4-acetamido-4'-isothiocyanostilbene-2,2'-sulfonic acid (SITS), which indirectly inhibits H+ secretion, was compared with cells additionally treated with 5 X 10(-4) M acetazolamide, an inhibitor of both H+ and HCO3- secretion. O2 consumption of MR cells treated with SITS alone was significantly greater than that of MR cells additionally treated with acetazolamide (delta = 0.56 +/- 0.10 microliter O2 X h-1 X mg protein-1, n = 6, P less than 0.003). There was no significant difference in G cells similarly treated. Another means of selectively altering H+ and HCO3- transports and their associated metabolic rates is to manipulate the Cl- concentration of the incubation medium. In a Cl(-)-rich medium, HCO3- and H+ transports are maximized. In low Cl(-)-SO2-4 medium, HCO3- secretion is selectively reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
Conductive properties of the rabbit outer medullary collecting duct: outer stripe
Authors: Koeppen B. M.
Published: December 2017

Segments of the outer medullary collecting duct were dissected from the outer stripe of the rabbit kidney (OMCDo) and perfused in vitro. The conductive properties of the tubule epithelium and individual cell membranes were determined by means of cable analysis and intracellular voltage-recording microelectrodes. The transepithelial voltage (VT) and resistance (RT) averaged -10.7 +/- 2.5 mV, lumen negative, and 28.5 +/- 2.9 k omega X cm (n = 27), respectively. Two cell types could be defined by their electrophysiological properties. One cell type (n = 7) had a mean basolateral membrane voltage (Vbl) of -30.1 +/- 2.4 mV, a fractional resistance of the apical membrane (fRa = Ra/Ra + Rbl) near unity (0.99 +/- 0.01), and a predominantly Cl(-)-selective basolateral cell membrane. The second cell type (n = 27) had a mean Vbl of -63.7 +/- 2.7 mV, a fRa of 0.81 +/- 0.02, and a predominantly K+-selective basolateral cell membrane. The present study focused on defining the conductive properties of this latter cell type. Amiloride (10(-5) M) and BaCl2 (2 mM) were used as probes of apical cell membrane Na+ and K+ conductive pathways, respectively. Amiloride increased fRa from 0.80 +/- 0.02 to 0.98 +/- 0.01 (n = 12), whereas BaCl2 increased fRa from 0.77 +/- 0.03 to 0.82 +/- 0.03 (n = 9). The conductive properties of the basolateral cell membrane were assessed by ion substitutions of the bath solution. A 10-fold increase in the bath [K+] depolarized Vbl by 34.9 +/- 1.9 mV (n = 16) in less than 1 s, indicating that this membrane was predominantly K+ selective.(ABSTRACT TRUNCATED AT 250 WORDS)
Patch-clamp technique in renal physiology
Authors: Palmer L. G.
Published: December 2017

The patch-clamp technique of Neher and Sakmann and their colleagues has been widely used over the last 5 years to investigate ion channels in excitable tissues. More recently, it has become useful as a tool to study channels involved in transepithelial ion transport. In this review, I briefly cover the basic concepts behind the patch-clamp technique and the kinds of information that can be obtained with it. I then summarize the applications of the technique to renal tissues and describe some of the channel types that have been observed to date in epithelia.
Autoregulation of renal blood flow in two-kidney, one-clip hypertensive rats
Authors: Iversen B. M. , Heyeraas K. J. , Sekse I. , Andersen K. J. , Ofstad J.
Published: December 2017

Renal blood flow (RBF) autoregulation was examined in the clipped and nonclipped kidneys in two groups of two-kidney, one-clip (2K-1C) hypertensive rats 10 wk after clipping. The arterial pressure distal to the clip and the renin secretion rate (RSR) were also examined. The blood pressure (BP) was 149 +/- 4 and 162 +/- 6 mmHg in the two hypertensive groups vs. 114 +/- 3 mmHg in the controls (P less than 0.02). The RBF (in ml X min-1 X kidney-1) was 4.27 +/- 0.41 in the nonclipped and 2.18 +/- 0.23 in the clipped kidneys (P less than 0.001). The pressure distal to the clip was 104 +/- 7 mmHg. The renal vascular resistance (RVR) (in mmHg X ml-1 X min-1 X g-1) was 25.0 +/- 1.4 in the control kidneys vs. 58.4 +/- 4.5 in the nonclipped (P less than 0.001) and 39.9 +/- 6.6 in the clipped kidneys (P less than 0.01). The RBF autoregulation was well preserved in the nonclipped kidneys but reset to a higher lower pressure limit of autoregulation of 106 +/- 4 mmHg, which was significantly higher than in the normotensive controls (84 +/- 6 mmHg) (P less than 0.01). In the clipped kidneys there was complete loss of RBF autoregulation. RSR decreased with reduction of the perfusion pressure in the clipped kidneys. The increased RVR might have been due to a combination of structural and functional changes in both kidneys.
Ca fluxes across duodenum and colon of spontaneously hypertensive rats: effect of 1,25(OH)2D3
Authors: Gafter U. , Kathpalia S. , Zikos D. , Lau K.
Published: December 2017

Calcium absorption by spontaneously hypertensive rats (SHR) was variably reported to be different from normotensive Wistar-Kyoto (WKY) controls. Furthermore, blunted responsiveness to the intestinal effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] has also been postulated. To evaluate this hypothesis, calcium fluxes were measured by the Ussing technique across duodenum and descending colon with or without prior 1,25(OH)2D3 treatment. Duodenal mucosal-to-serosal calcium flux (Jm----s) (44.9 vs. 52.4 nmol X cm-2 X h-1), serosal-to-mucosal flux (Js----m) (25.6 vs. 28.4 nmol X cm-2 X h-1), and net flux (Jnet) were comparable. 1,25(OH)2D3 increased duodenal Jm----s in both SHR and WKY groups (95.2 and 86.8 nmol X cm-2 X h-1). Js----m was lower in SHR (26.1 vs. 35.6 nmol X cm-2 X h-1, P less than 0.01), although the tendency for a higher Jnet in SHR (68.6 vs. 51.2 nmoles X cm-2 X h-1) was statistically insignificant. Short-circuit current was higher in the colon of SHR, both before and after 1,25(OH)2D3, suggesting increased sodium transport. Basal colonic Jnet was virtually zero in both groups but comparably increased by 1,25(OH)2D3 because of stimulation in only Jm----s. Prevention of hypertension by hydralazine since the 4th wk of age did not alter the findings compared with the hypertensive SHR, suggesting calcium transport rates were unaffected by hypertension. These data indicate that in vitro, duodenal, and colonic active calcium transport by the SHR is similar to WKY. Their normal responses to 1,25(OH)2D3 do not support the hypothesis of intestinal resistance.
Effect of atrial natriuretic factor on adenylate cyclase in various nephron segments
Authors: Anand-Srivastava M. B. , Vinay P. , Genest J. , Cantin M.
Published: December 2017

The effects of rat synthetic atrial natriuretic factor (ANF) [Arg101, Tyr126] were studied on adenylate cyclase activity in various renal structures such as glomeruli, proximal tubules, loops of Henle, and collecting ducts from dog kidney. ANF inhibited adenylate cyclase activity in glomeruli, loops of Henle, and collecting ducts, but not in proximal tubules, in a concentration-dependent manner. The maximal inhibitions observed were approximately 45% in glomeruli and collecting ducts with an apparent Ki of 10(-10)-10(-9) M and 30% in loops of Henle with an apparent Ki of 10(-11)-5 X 10(-10) M. ANF also inhibited the stimulatory responses of various hormones and forskolin on adenylate cyclase in glomeruli, collecting ducts, and loops of Henle. However, the extent of inhibition varied in the three fractions. In addition, ANF showed an additive effect with the inhibitory response of angiotensin II on adenylate cyclase in glomeruli. These data indicate that ANF receptors coupled to adenylate cyclase are present in glomeruli, loops of Henle, and collecting ducts and not in proximal tubules, and it can be suggested that the inhibition of adenylate cyclase by ANF may be one of the mechanisms through which ANF regulates kidney functions.
Effects of inhibitors of Cl conductance on Cl self-exchange in rabbit cortical collecting tubule
Authors: Tago K. , Warden D. H. , Schuster V. L. , Stokes J. B.
Published: December 2017

Electroneutral vs. conductive pathways of Cl transport were examined by measuring transepithelial conductance (GT) and the lumen-to-bath 36Cl rate coefficient (KCl). Experimental conditions minimized both Cl-HCO3 exchange [HCO3/CO2-free, N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid (HEPES)-buffered solutions] and the electrical driving force for paracellular Cl diffusion (amiloride in the perfusate, transepithelial voltage near zero). Two agents known to inhibit Cl conductances in other epithelia, anthracene-9-carboxylate (9AC, 1 mM) and diphenylamine carboxylate (DPC, 0.1-0.5 mM) reversibly reduced GT and KCl when added to the bath. Both reduced KCl to values consistent with paracellular diffusion. Bath DPC had no effect on GT in the presence of 4 mM lumen Ba2+, suggesting that the DPC-sensitive conductance is in series with an apical K conductance, i.e., resides on the basolateral membrane. Lumen DPC also reduced GT and KCl, but was less potent than bath DPC. Because the lumen DPC effect on GT was also blocked by lumen Ba2+, lumen DPC probably inhibits a basolateral Cl conductance. K removal and ouabain (0.5 mM) had no effect on KCl, suggesting that Cl tracer movement is not predominantly through the principal cell. We assume that these agents are inhibiting Cl conductive pathways and propose a model in which transcellular Cl movement through the intercalated cell occurs via an apical electroneutral entry step in series with a basolateral conductive pathway.