bluuebunny/crossref_metadata_2025 huggingface dataset:
Dibucaine stimulation of p-aminohippurate accumulation in rat kidney cortical slices
Authors: Nakajima M. , Nakano S. , Gemba M.
Published: December 2017

We studied the effects of dibucaine on p-aminohippurate (PAH) transport using rat kidney cortical slices. Addition of dibucaine in concentrations from 0.01 to 0.1 mM stimulated PAH accumulation in a concentration-dependent way; at higher concentrations, accumulation was inhibited. Kinetic studies showed that dibucaine increased the apparent maximal activity of PAH transport, whereas the apparent Km remained essentially constant. The efflux of PAH from the slices was significantly depressed by the drug. Dibucaine had no significant effect on the sodium gradient, medium to intracellular fluid. The drug had biphasic effects on hypotonic hemolysis; at lower concentrations (up to 0.2 mM) it protected erythrocytes, and at much higher concentrations, it has a lytic effect. The pattern of the membrane-stabilizing action of dibucaine was similar to that of the stimulation of PAH accumulation. These results indicate that dibucaine markedly stimulated accumulation of PAH. Stimulation by this drug of PAH transport cannot be explained by the increase in the sodium gradient; it may be due at least in part to membrane stabilization.
Dynamic response of PG synthesis to peptide hormones and osmolality in renal tubular cells
Authors: Wuthrich R. P. , Loup R. , Favre L. , Vallotton M. B.
Published: December 2017

A superfusion technique was adapted to collagenase-dispersed renal medullary and cortical tubular cells to study prostaglandin (PG) synthesis in response to arginine vasopressin (AVP), angiotensin II (ANG II), bradykinin (BK), Ca2+ ionophore A23187, and to changes in osmolality. Medullary and cortical cells promptly responded to the stimuli by an increase in PGE2 and PGF2 alpha production, whereas 6-keto-PGF1 alpha was not detected. AVP and BK were active on medullary cells, and ANG II was active mainly on cortical cells. A23187 stimulated PG synthesis in both cells but predominantly in the medulla. PG synthesis was dependent on the presence of extracellular Ca2+. The Ca2+ entry blocking agents verapamil and lanthanum did not inhibit the PG response to AVP, BK, and ANG II. Thus peptide hormone-stimulated PG synthesis in renal tubular cells did not depend on Ca2+ influx through channels blocked by these agents. Hyperosmolar NaCl or mannitol stimulated PG synthesis in cortical and, more markedly, in medullary cells. Hyperosmolar urea inhibited PGE2 synthesis stimulated by peptide hormones, NaCl, and A23187 in both cell preparations. In conclusion, the superfusion of isolated tubular cells is a useful method to study the dynamic aspects of renal PG release in response to various sequentially applied stimuli.
Effects of atrial natriuretic peptide on renin secretion in nonfiltering kidney
Authors: Opgenorth T. J. , Burnett J. C. , Granger J. P. , Scriven T. A.
Published: December 2017

Studies were performed in normal dogs (n = 6) and dogs with nonfiltering kidneys (n = 8) to determine the effects of synthetic atrial natriuretic peptide (ANP) on renin secretion and renal hemodynamics in the presence and absence of a functional macula densa. In normal dogs, intrarenal infusion of ANP (0.3 microgram X kg-1 X min-1) resulted in a decrease in renin secretion from 325.5 +/- 87.4 to 52.4 +/- 29.4 ng/ml, despite a sustained decrease in arterial pressure. In contrast, in the nonfiltering kidney without a functional macula densa, ANP infusion did not inhibit renin secretion in this nonfiltering model. Adenosine, however, known to directly inhibit renin secretion, did decrease renin secretion in this nonfiltering model. The present studies document that, in the nonfiltering kidney, ANP has no inhibitory effect on renin secretion.
Effects of leukotrienes on isolated rat glomeruli and cultured mesangial cells
Authors: Barnett R. , Goldwasser P. , Scharschmidt L. A. , Schlondorff D.
Published: December 2017

Several vasoactive substances influence glomerular function in vivo and alter glomerular surface area and prostaglandin (PG) synthesis in vitro. Leukotrienes (LT) LTC4 and LTD4 may also influence glomerular function in vivo and in the isolated perfused kidney. We therefore compared the effects of LT with those of angiotensin II (ANG II), arginine vasopressin (AVP), and platelet activating factor (PAF) on planar surface area of isolated rat glomeruli and the shape change of cultured mesangial cells and their PG synthesis. ANG II, AVP, and PAF decreased the surface area of isolated rat glomeruli by 10-14% with comparable changes induced by LTC4 and LTD4. Half-maximal effects of LTs were observed at approximately 10(-7) M. Incubation of cultured rat mesangial cells with LTC4 or LTD4 at 10(-7) and 10(-8) M was also associated with shape changes of the cells resulting in significant reductions in planar surface area in a dose- and time-dependent fashion similar to that noted previously with other vasoactive agents. In cells grown on a flexible silicone rubber support, LTD4 resulted in rapid increases in wrinkling of the mobile surface indicating that the shape change may represent cell contraction. The LT-mediated decrease in surface area of glomeruli and mesangial cells was partially antagonized by the LT inhibitor FPL-55712. In contrast to the 11- and 7-fold enhancement of PGE2 synthesis in cultured mesangial cells by ANG II or PAF, neither LTC4 nor LTD4 affected PGE2 production. These results demonstrate that LTC4 and LTD4 cause mesangial shape changes that in the whole glomerulus may decrease glomerular surface area.(ABSTRACT TRUNCATED AT 250 WORDS)
Dopamine receptors modulate sodium excretion in denervated kidney
Authors: Jose P. A. , Felder R. A. , Holloway R. R. , Eisner G. M.
Published: December 2017

Dopamine (DA) modulates sodium excretion by the innervated kidney. To examine the role of DA in the denervated (DNX) kidney the effects of the DA1/DA2 antagonist cis-flupenthixol (group 2, n = 7) (10 nmol X kg-1 X min-1), given intravenously in saline-loaded Wistar-Kyoto rats after acute unilateral left DNX, were compared with a placebo group (group 1, n = 7) and a group that received the DA1 antagonist SCH 23390 (group 3, n = 7) at 2.5 nmol X kg-1 X min-1. Pentobarbital sodium anesthesia was employed. Adequacy of DNX was assessed by a natriuresis and decrease in renal norepinephrine content in the DNX kidney and an antinatriuresis in the innervated right kidney. Mean arterial pressure slightly decreased in the placebo group (group 1, 106.7 +/- 2.2 vs. 99.3 +/- 2.4 mmHg) and after cis-flupenthixol (group 2, 108.8 +/- 2.7 vs. 92.8 +/- 1.8 mmHg) but not after SCH 23390 (group 3, 105.6 +/- 1.6 vs. 103 +/- 1.1 mmHg). Glomerular filtration rate was not affected by placebo or SCH 23390 in the DNX or innervated kidney but did slightly decrease after cis-flupenthixol in the DNX kidney. Sodium and water excretion after drug administration differed among the groups. In the DNX kidney urine flow decreased only in group 2, whereas fractional sodium excretion decreased modestly (P less than 0.05 paired t test) with SCH 23390 (3.53 +/- 0.34 vs. 2.89 +/- 0.20%) markedly with cis-flupenthixol (3.18 +/- 0.50 vs. 1.21 +/- 0.18%) and was unchanged in the placebo group (3.25 +/- 0.61 vs. 3.45 +/- 0.45%).(ABSTRACT TRUNCATED AT 250 WORDS)
Activities of cathepsins B and L in isolated nephron segments from proteinuric and nonproteinuric rats
Authors: Olbricht C. J. , Cannon J. K. , Garg L. C. , Tisher C. C.
Published: December 2017

The intralysosomal proteinases cathepsins B and L were measured in microdissected segments of rat nephron. Z-Arg-Arg-NMec served as the substrate for cathepsin B and Z-Phe-Arg-NMec for cathepsin B and L together. Individual S1, S2, and S3 segments of proximal tubules, TDL, MTAL, CTAL, DCT, CCD, and OMCD were dissected from young female rats weighing 130 +/- 11 g with low protein excretion (0.68 +/- 0.1 mg/24 h), from older female rats weighing 289 +/- 9 g with protein excretion of 10 +/- 6.3 mg/24 h, from older male rats weighing 404 +/- 11 g with protein excretion of 22 +/- 6 mg/24 h, from female rats weighing 198 +/- 10 g with albumin-induced proteinuria (411 +/- 134 mg/24 h), and from female rats weighing 203 +/- 11 g with low protein excretion (2.7 +/- 0.4 mg/24 h). The distributions of cathepsin activities along the nephron were similar. In all five groups, S1 and S2 segments had enzyme activities three times higher than in all remaining segments. In S2 and S3, enzyme activities were two to three times higher in proteinuric animals. These findings suggest that in proteinuric animals the increase in the protein load delivered to the proximal tubules selectively stimulated cathepsin activities in the S2 and S3 segments, presumably because of an increase in protein uptake, and that cathepsins B and L participate in lysosomal digestion of protein reabsorbed from the glomerular filtrate via endocytosis.
Effect of atriopeptin II on determinants of glomerular filtration rate in the in vitro perfused dog glomerulus
Authors: Fried T. A. , McCoy R. N. , Osgood R. W. , Stein J. H.
Published: December 2017

Atrial natriuretic factor (ANF) is a peptide originally found to be present in extracts of mammalian atria that possess marked natriuretic and diuretic qualities. A number of mechanisms have been suggested to explain these properties. Recently, it has been suggested that ANF may enhance glomerular filtration. In this report, we describe a series of experiments designed to investigate if atriopeptin II, a 23-amino acid synthetic analogue of ANF, increases glomerular filtration rate (GFR) and, if so, the mechanism for this increase. We used the isolated perfused glomerulus technique (n = 6), which allows a single isolated glomerular unit to be perfused and the determinants of single-nephron GFR (SNGFR) to be measured. Two periods were performed in each experiment, the control followed by the experimental. The only difference between the two periods was the addition of atriopeptin II to the experimental perfusate at a final concentration of 5 X 10(-7) M. There was indeed a significant increase in the SNGFR (78 +/- 27 to 108 +/- 29 nl/min, P less than 0.01). This increase was associated with a significant increase in the glomerular capillary hydrostatic pressure (PGC) from 31 +/- 3 to 35 +/- 3 mmHg (P less than 0.05). The filtration fraction also increased in each experiment (from 0.16 +/- 0.3 to 0.25 +/- 0.03, P less than 0.005). Neither the afferent flow nor the efferent arteriolar flow changed, although there was a tendency for both to decrease.(ABSTRACT TRUNCATED AT 250 WORDS)
Production of platelet-activating factor in glomeruli and cultured glomerular mesangial cells
Authors: Schlondorff D. , Goldwasser P. , Neuwirth R. , Satriano J. A. , Clay K. L.
Published: December 2017

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) results in contraction of isolated glomeruli and cultured mesangial cells and concomitantly causes release of arachidonic acid and prostaglandin E2 (PGE2) formation. The kidney and isolated glomeruli can also generate material that has PAF bioactivity. We therefore examined the capacity of isolated renal glomeruli and cultured glomerular mesangial cells from rats to form PAF. Both isolated glomeruli and cultured mesangial cells transformed 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine ([3H]lyso-PAF) into a labeled product comigrating both on thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC) with authentic PAF. Using rabbit platelet aggregation as bioassay for PAF, we found that isolated glomeruli produced 4 +/- 2 pmol/mg glomerular protein of PAF-like material, and mesangial cells produced 30 +/- 8 pmol/mg cell protein when stimulated with A23187 (10(-5) M) for 30 min. The major species of the PAF material produced by mesangial cells was identified as 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine after HPLC separation, followed by fast atom bombardment and gas chromatography-mass spectrometry. These results show that glomerular mesangial cells can produce PAF, which could contribute locally to the regulation of glomerular function.
Handling of dopamine and dopamine sulfate by isolated perfused rat kidney
Authors: Buu N. T. , Duhaime J. , Kuchel O.
Published: December 2017

The possible contribution of circulating dopamine sulfate to urinary free dopamine and the synthesis of norepinephrine by the renal nerves were examined in the isolated perfused rat kidney. Perfusion of the kidney with dopamine sulfate did not yield significant amounts of free dopamine indicating that, unlike L-dopa, dopamine sulfate is not a good source of urinary free dopamine. The excretion of dopamine sulfate was slower than or comparable with that of free dopamine, suggesting that sulfoconjugation is not a mechanism to facilitate the excretion of free dopamine. Unlike free dopamine, dopamine sulfate was not metabolized by renal catechol-O-methyltransferase or monoamine oxidase. Perfusion of L-dopa and free dopamine led to the generation of norepinephrine in the kidney. This synthesis was abolished when the kidney was denervated, suggesting that the renal nerves were the main sites of the norepinephrine synthesis. Both norepinephrine and dopamine were rapidly metabolized by catechol-O-methyltransferase and monoamine oxidase, but renal phenolsulfotransferase appeared to have no action on the catecholamines.
Prostaglandin E2 but not I2 restores furosemide response in indomethacin-treated rats
Authors: Kirchner K. A. , Martin C. J. , Bower J. D.
Published: December 2017

Indomethacin attenuates furosemide's natriuretic response. Although this has been attributed to cyclooxygenase inhibition, attempts to correlate prostaglandin (PG) production with furosemide's natriuresis have led some investigators to conclude that prostaglandins are not involved in this response. This study was designed to evaluate the effects of intraaortic administration of PGE2, PGI2 (100 ng X kg-1 X min-1), or the vasodilators secretin or bradykinin (75 microU X kg-1 X min-1) on the furosemide-indomethacin antagonism. Fractional sodium excretion (FENa) during furosemide administration was 4.59 +/- 0.50% in control rats but 1.84 +/- 0.33% in indomethacin-treated rats (Indo) (P less than 0.001). PGE2 prevented indomethacin from attenuating furosemide's response (FENa, 3.91 +/- 0.25%; P = NS vs. control; P less than 0.01 vs. Indo). PGI2, however, failed to prevent the furosemide-indomethacin antagonism (FeNa, 1.94 +/- 0.59%, P less than 0.001 vs. control; P = NS vs. Indo). Inulin clearance, arterial pressure, filtered sodium load, and renal blood flow were not different between groups. Neither secretin nor bradykinin prevented the indomethacin-furosemide antagonism. This study is consistent with the hypothesis that indomethacin antagonizes furosemide's natriuretic response by prostaglandin synthesis inhibition. Furthermore, PGE2 seems to restore furosemide's response through actions other than a vasodilatory effect.
Kinetic analysis of rat renal tubular transport based on multiple-indicator dilution method
Authors: Itoh N. , Sawada Y. , Sugiyama Y. , Iga T. , Hanano M.
Published: December 2017

New methods, based on the multiple-indicator dilution (MID) technique, to study the kinetic relations between the renal tubular cell entry process and the secretory process of drugs are proposed. [3H]Cimetidine was used as a model drug. T-1824-labeled albumin (a vascular reference), [14C]creatinine (an extracellular reference), and [3H]cimetidine were rapidly injected into the renal artery of isolated perfused rat kidney, and normalized outflow-time patterns were secured from rapidly sampled renal venous perfusate. A distributed two-compartment model was fitted to the dilution data by nonlinear least-squares regression, and the influx, efflux, and sequestration rate constants were estimated. Both the influx and the sequestration process (based on the unbound cimetidine concentration) had two transport systems (i.e., Michaelis-Menten-type saturable transport and linear-type passive transport), whereas the efflux process was independent of the intracellular cimetidine concentration. At the low dose of cimetidine the influx clearance was larger than those of the efflux and sequestration, whereas at the high dose no remarkable difference was observed among these three clearances due to the large decrease in the influx clearance. Thus the MID technique is a sensitive new method to study the rate-limited process of renal tubular transport in rats.
Renin release from different parts of rat afferent arterioles in vitro
Authors: Baumbach L. , Skott O.
Published: December 2017

A technique was designed to study renin release from superfused rat glomeruli with short attached arterioles (SAG), from single glomeruli with long attached arterioles (LAG), and from single afferent arterioles (AA). The preparations obtained by magnetic isolation and microdissection were superfused individually, and the renin release was measured by an ultramicroradioimmunoassay with a detection limit of 3 X 10(-9) Goldblatt units. The renin content of one SAG was about one-fifth of that contained in one AA. Isoprenaline (10(-5) M) did not change renin release from SAG, whereas renin release from AA and LAG increased threefold (P less than 0.01). A 30-mosmol/kg reduction in medium sodium chloride concentration increased renin release from SAG 50% (P less than 0.01). This challenge caused no change in renin release from AA. It is concluded that the isoprenaline-sensitive juxtaglomerular (JG) cells are located in the afferent arteriole only at some distance from the glomerulus, whereas those cells sensitive to sodium chloride are located within and/or close to the glomerulus.
Role of arginine vasopressin in fetal renal response to hypertonicity
Authors: Woods L. L. , Cheung C. Y. , Power G. G. , Brace R. A.
Published: December 2017

We studied the effects of hyperosmolality on fetal renal function and the role of arginine vasopressin (AVP) in these responses. NaCl (9%) was injected intravenously into chronically catheterized ewes and their fetuses, followed by a continuous infusion of 9% NaCl into the ewes. The fetuses were either normal, infused with AVP, or infused with an AVP antagonist. In normal fetuses NaCl injection caused fetal and maternal blood osmolalities to be elevated by 10-15 mosmol/kg for 4 h with no change in fetal blood volume; fetal plasma AVP rose 42%. Fetal arterial pressures rose transiently by 2-10 mmHg. Fetal urine flow rose transiently by 73% after NaCl injection and then averaged 27% below control after 1 h, whereas fetal urine osmolality increased from 188 +/- 31 to 282 +/- 33 mosmol/kg. In a second group of fetuses AVP infusion alone caused fetal urine osmolality to increase by 123 +/- 39 mosmol/kg and urine flow to fall 31%, whereas in a third group the antagonist alone had no effect on urine flow or osmolality. After hypertonic injection into fetuses infused with AVP or the antagonist, the transient changes were similar to those in normal fetuses. However, the sustained increase in urine osmolality and decrease in flow after hypertonic injection were abolished in AVP-infused and antagonist-infused fetuses. Thus it appears that the transient changes in fetal renal function after hypertonic injection are not AVP-induced and may be due to transient increases in arterial pressure, whereas the prolonged changes in urine flow and osmolality appear to be mediated by increases in fetal plasma AVP levels.
System A amino acid transport in incubated muscle: effects of insulin and acute uremia
Authors: Maroni B. J. , Karapanos G. , Mitch W. E.
Published: December 2017

The insulin-stimulated increase in amino acid uptake in most cells and tissues involves stimulation of system A transport. In muscle the probes used to study this process have not been specific, making it difficult to determine whether system A is abnormal in insulin-resistant states, such as acute renal failure (ARF). To circumvent this problem, we studied 2-(methylamino) isobutyrate (MeAIB) transport. Its specificity for system A in incubated rat epitrochlearis muscles was documented by showing its uptake by only one carrier that is sodium dependent and insulin responsive and that exhibits adaptive regulation in response to starvation. Using this specific probe we determined whether insulin-stimulated amino acid transport by system A is impaired by ARF. MeAIB uptake was linear for 3 h in muscles of ARF and sham-operated (SO) rats. In the absence (basal) or presence of insulin, MeAIB uptake was significantly lower in ARF, yet the stimulation by insulin was similar in both groups. Likewise, the insulin dose-response relationship confirmed that physiological levels of insulin (less than or equal to 10(2) microU/ml) increased transport by a similar degree. At greater than or equal to 10(2) microU/ml insulin there was a plateau in MeAIB transport in ARF but not in SO muscles. Thus basal system A transport is depressed in ARF, but the stimulation of system A by physiological levels of insulin is preserved. At pharmacological levels of insulin system A transport is impaired by ARF.
System ASC and sodium-independent neutral amino acid transport in muscle of uremic rats
Authors: Maroni B. J. , Karapanos G. , Mitch W. E.
Published: December 2017

Neutral amino acids are transported by systems A, ASC, and L. In the previous companion study we demonstrated that 2-(methylamino) isobutyrate (MeAIB) is a specific substrate for system A in muscle and that stimulation of system A by physiological concentrations of insulin is preserved in acute uremia (ARF). Insulin-stimulated uptake of the nonspecific probes cycloleucine and alpha-aminoisobutyrate (AIB) is reportedly blunted by uremia; the cause of this and whether transport by systems ASC and L is defective are unknown. In this study we examined these questions using incubated epitrochlearis muscles from normal fed, ARF, and sham-operated control (SO) rats. System ASC was studied by measuring AIB and cycloleucine uptake in the presence of inhibitors of systems A and L, MeAIB and 2-amino-2-norbornane carboxylic acid (BCH), respectively. System L was defined as sodium-independent uptake suppressible by BCH. Excess MeAIB completely inhibited insulin-stimulated AIB and cycloleucine uptake, indicating that system A is the only insulin-responsive neutral amino acid carrier in muscle. In ARF and SO mucles both AIB and cycloleucine uptake were indistinguishable in the absence or presence of insulin. Moreover, ARF caused no detectable abnormality in transport by systems ASC and L.
Effects of parathyroid hormone on cytosolic calcium in renal proximal tubular primary cultures
Authors: Hruska K. A. , Goligorsky M. , Scoble J. , Tsutsumi M. , Westbrook S. , Moskowitz D.
Published: December 2017

The effects of parathyroid hormone on the cytoplasmic Ca2+ concentration of canine renal proximal tubule cells grown in primary culture were determined using the fluorescent Ca2+ indicator quin 2. The cultured cells exhibited responses to hormones, enzyme activities, transport functions, and morphology characteristic of the proximal convoluted tubule. Parathyroid hormone stimulated an immediate rise in cytoplasmic Ca2+, both in suspended cells and cells studied as a monolayer on Nuclepore filters. The rise in cytoplasmic Ca2+ induced by the hormone was sustained for 15-30 min, was dose dependent, and was not mimicked by cyclic AMP. Removing Ca2+ from the extracellular media markedly decreased cytoplasmic Ca2+ and abolished the effects of parathyroid hormone on cytosolic Ca2+. 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate blocked the effects of the hormone on cytosolic Ca2+, but mitochondrial uncouplers failed to inhibit the effects of the hormone to increase cytoplasmic Ca2+. These studies support a role of Ca2+ in the activation of proximal renal tubule cells by parathyroid hormone.
Regulation of renal Na+-K+-ATPase in the rat: role of increased potassium transport
Authors: Mujais S. K. , Chekal M. A. , Hayslett J. P. , Katz A. I.
Published: December 2017

The purpose of this study was to characterize the alterations in collecting tubule Na+-K+-ATPase activity produced by sustained increments in dietary potassium in the rat and to evaluate the role of aldosterone in their generation. In adrenal-intact animals, feeding a high-potassium diet (10-fold that of control) or administration of a high physiological dose of aldosterone (5 micrograms X 100 g-1 X day-1), which simulates the delivery rate of this hormone during potassium loading (both for 7 days), caused marked increments in Na+-K+-ATPase activity in the cortical collecting tubule (CCT) but had no effect on the enzyme in the inner stripe of the medullary collecting tubule (MCT). A significant increase in enzyme activity was also observed after smaller dietary potassium increments (2.5 and 5 times the control) and after 4 (but not 2) days of dietary potassium load. In adrenalectomized rats provided with physiological replacement doses of corticosterone and aldosterone (0.8 micrograms X 100 g-1 X day-1), Na+-K+-ATPase activity in both CCT and MCT was similar to that of adrenal-intact controls but remained unchanged after 7 days on the potassium-enriched (10-fold) diet. In contrast, adrenalectomized animals receiving the high physiological dose of aldosterone displayed an increase in Na+-K+-ATPase activity of CCT comparable with that of adrenal-intact animals, whereas the enzyme activity in the MCT was unaffected. In conclusion, 1) following chronic potassium loading Na+-K+-ATPase activity increases significantly in the CCT with no change in its activity in the inner stripe of the MCT.(ABSTRACT TRUNCATED AT 250 WORDS)
Basolateral membrane properties of juxtamedullary proximal tubule in newborn rabbit
Authors: Linshaw M. A. , Welling L. W. , Bauman C. A.
Published: December 2017

We have evaluated the functional and morphological changes that occur in juxtamedullary proximal convoluted tubules before and after the completion of nephrogenesis at approximately 3 wk of age. Tubules were dissected in connection with glomeruli in the deep juxtamedullary zone, crimped at both ends, and induced to swell in isotonic medium by sequential exposure to ouabain, reduced bath protein concentration, and collagenase. Basolateral membrane surface areas were measured morphometrically in paired tubules if possible. The swelling rates and basolateral areas were the same in tubules from 2-7- and 14-17-day-old rabbits (during nephrogenesis), had increased in 28-42-day-old rabbits (after nephrogenesis), and increased further in adults. Because the surface areas and swelling rates increased proportionally, the nephrons “matured” only after nephrogenesis was complete and then only in basolateral surface area. The intrinsic membrane properties of hydraulic conductivity and ion permeability apparently remained constant.
Action of ADH on isolated medullary thick ascending limb of the Brattleboro rat
Authors: Besseghir K. , Trimble M. E. , Stoner L.
Published: December 2017

Establishment of a maximal corticomedullary osmotic gradient during chronic administration of arginine vasopressin (antidiuretic hormone, ADH) to Brattleboro (diabetes insipidus, DI) rats is a gradual process. The effects of ADH on voltage and radioisotopic chloride efflux (lumen to bath) were investigated in medullary thick ascending limb (mTAL) isolated from DI rats and perfused in vitro. Acute in vitro exposure of mTAL to ADH (250 microU/ml) significantly increased both the voltage (+3.3 +/- 0.3 to +4.5 +/- 0.5 mV) and chloride efflux (192.7 +/- 29.4 to 240.4 +/- 41.5 peq/min X mm). After chronic in vivo treatment with ADH for 10-21 days mTAL expressed substantially higher basal voltage and chloride efflux (+8.4 +/- 0.6 mV and 393.2 +/- 71.6 peq/min X mm). Acute in vitro application of ADH to mTAL from chronically treated animals induced a further small increase in voltage (22%). These results are taken to indicate that ADH may have dual effects on NaCl transport by the mTAL of the DI rat: a small rapid effect, and a larger long-term increase in transport that can be shown only after chronic administration of ADH. These effects may, in part, explain the gradual enhancement of concentrating ability observed in DI rats.
Electrophysiology of salamander proximal tubule. I. Effects of rapid cooling
Authors: Sackin H.
Published: December 2017

The response of the amphibian proximal tubule to a rapid decrease in temperature was studied in isolated perfused tubules of Ambystoma tigrinum. Cooling from 23 to 4 degrees C increased paracellular and cellular electrical resistances by factors of 1.7 and 3.6, respectively, but had virtually no effect on the ionic selectivity of the paracellular pathway. When lumen and bath solutions were maintained identical by rapid tubule perfusion, decreasing bath temperature from 22 to 0 degree C in 400 ms depolarized the transepithelial potential (Vte) from -3.7 +/- 0.3 to -1.1 +/- 0.2 mV and depolarized the basolateral membrane potential (Vbl) from -52 +/- 3 to -45 +/- 3 mV (n = 12). These fast depolarizations were followed by slower depolarizations of both Vte and Vbl that continued throughout the period of low temperature. Only approximately 30% of the initial slow depolarization of Vte at low temperature could be explained by changes in electrical resistance and cell membrane potential. The remaining 70% of this Vte depolarization at low temperature is consistent with equilibration of a hypertonic interspace with isotonic lumen and bath solutions. Given the anion selectivity of Ambystoma proximal tubule, the magnitude of this slow Vte depolarization implies an interspace NaCl concentration 2-5% higher than the NaCl concentration in either the lumen or bath solutions.
Effect of age on renal conservation of phosphate in the rat
Authors: Kiebzak G. M. , Sacktor B.
Published: December 2017

Renal handling of phosphate (Pi) was examined in male Wistar-derived rats, 2-3, 6, 12, 18, and 24 mo of age. We observed a significant age-related phosphaturia [i.e., elevated urinary excretion (UPi V) and fractional excretion (FEPi)] in rats fed a normal phosphorus diet (NPD; 0.5% Pi). Concomitantly, plasma Pi decreased significantly and progressively with age. The mechanism of this age-related decrement in Pi conservation was examined by determining the initial (5 s) rate of Na+ gradient-dependent uptake of Pi in renal brush-border membrane vesicles (BBMV). Pi uptake significantly declined with increasing age. No consistent age-related decrease was seen in the Na+ gradient-dependent uptakes of glucose and proline by the same BBMV preparations, demonstrating the specificity of the Pi transport decrement. Pi transport kinetics revealed a significant age-related decrease in Vmax. No difference in Km of Pi was seen between age groups. These kinetic findings suggest either a decreased number of Pi carriers or decreased turnover of Pi carriers. Elevated parathyroid hormone did not explain the alteration in Pi conservation since urinary cAMP was not elevated in the intact senescent rat, and Pi uptake was not normalized in 24-mo-old rats 3 days after parathyroidectomy. The senescent 24-mo-old rat as well as the young adult 6-mo-old animal adapted to a low-phosphorus diet (LPD; 0.1% Pi) with a striking (greater than 100%) increase in Pi uptake by BBMV compared with NPD. thus the senescent kidney retained the capacity to respond appropriately to a LPD.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of vasopressin on ependymal and capillary permeability to tritiated water in cat
Authors: Rosenberg G. A. , Kyner W. T. , Fenstermacher J. D. , Patlak C. S.
Published: December 2017

Ependymal cells line the cerebral ventricles forming the interface that separates the cerebrospinal (CSF) and interstitial fluids (ISF). Extracellular molecules move between ependymal cells, whereas lipid soluble molecules pass both between and through cells. We measured the transfer of tritiated water (TOH) from CSF to blood across the ependymal and capillary interfaces by ventriculocisternal (VC) steady-state tissue clearance. Adult cats anesthetized with pentobarbital sodium underwent VC perfusion with the extracellular marker [14C]sucrose and TOH added to the artificial CSF. Brain tissue was analyzed for depth of penetration of the isotopes into periventricular gray matter. We found that TOH distribution space was lower than expected from water content measurements, whereas sucrose space was normal. Using VC steady-state equations we calculated an ependymal permeability that was similar to the permeability of the cerebral capillary. When arginine vasopressin (AVP) was added to the perfusate in different amounts, both capillary transfer times and ependymal permeability increased. Our results show that the ependyma may be important in water movement in the brain and support the suggestion that AVP influences water exchange in mammalian brain tissue.
Renal response of newborn dog to potassium loading
Authors: Lorenz J. M. , Kleinman L. I. , Disney T. A.
Published: December 2017

The renal response to potassium loading was studied in 14 newborn (6-20 days of age) and 14 adult mongrel dogs in order to determine the capacity of the newborn to excrete potassium load. Eight newborn and eight adult dogs were infused with 20 mueq of potassium chloride X min-1 X kg body wt-1 for 240 min. Adults excreted a significantly greater proportion of the potassium load during the 240-min infusion than did newborns (72 +/- 4 vs. 52 +/- 4%, P = 0.003). The infusion resulted in a significantly greater increase in plasma potassium concentration in the newborn (3.9 +/- 0.3 meq/liter) than in the adult (2.8 +/- 0.4 meq/liter), P = 0.05. Average potassium excretion rate per body weight was greater in the adult than newborn during potassium loading (15.0 +/- 1.0 vs. 10.4 +/- 0.7 mu eq X min-1. kg body wt-1, P = 0.003); however, average potassium excretion corrected for glomerular filtration rate was not significantly different between the adult and newborn (3.2 +/- 0.2 vs. 3.0 +/- 0.2 mu eq/ml filtered, P greater than 0.20). In another six newborn and six adult dogs, blockade of distal nephron potassium secretion with amiloride in the potassium-loaded state inhibited more than 90% of potassium excretion in both the newborn and adult.(ABSTRACT TRUNCATED AT 250 WORDS)
Renal tissue citrate: independence from citrate utilization, reabsorption, and pH
Authors: Anaizi N. H. , Cohen J. J. , Black A. J. , Wertheim S. J.
Published: December 2017

During alkalosis in vivo, renal tissue [citrate] [( citrate]t) increases and citrate reabsorption (Tcit) and utilization (Qcit) simultaneously decrease. The decrease in Qcit is interpreted to cause the increased [citrate]t, which in turn decreases Tcit X Renal citrate handling and [citrate]t could be regulated by other mechanisms, since alkalosis changes [substrate] and [H+] in extracellular (ECF) and intracellular (ICF) fluid. Also, since high plasma [citrate] decreases ionized [Ca2+] (Cai), it is not possible to determine in vivo whether there is a maximum for Tcit or Qcit and whether change in extracellular fluid (delta ECF) pH affects these maxima. We perfused the substrate-limited isolated rat kidney for either 110 (n = 36) or 50 min (n = 44) at pH 7.2, 7.4, or 7.6; pH was changed by varying [HCO3-]; Cai was held constant at approximately 2.5 meq/liter. When citrate was the only substrate available in a Krebs-Ringer-HCO3 perfusate containing 6% substrate-free albumin, both Qcit and Tcit had maximal rates: Qcit much greater than Tcit; at pH 7.6, Qcit and Tcit were significantly reduced below their values at pH 7.2 or 7.4. In contrast to in vivo observations, [citrate]t was not significantly increased at high ECF pH. To test whether [citrate]t in the perfused kidney can increase in alkalosis, 11 additional perfusions were done in the presence of glucose plus lactate plus malate but without added citrate: [citrate]t = 0.6 mumol X g-1 at pH 7.6 and 0.3 mumol X g-1 at pH 7.2 (P less than 0.01); no citrate was detectable in the perfusate, and urinary citrate excretion was negligible. Thus, in the isolated rat kidney, an increase in [citrate]t occurred in alkalosis and was derived from precursors and not from citrate in the ECF. Overall, when only citrate was available to the isolated kidney during alkalosis, a significant rise in [citrate]t did not occur, although Vmax for Tcit and Qcit decreased. These effects of alkalosis on Tcit are consistent with observations in brush-border vesicles, where divalent citrate is the preferential substrate for luminal Na+-coupled transport; by contrast, high ECF pH and [HCO-3] apparently decrease Qcit by a direct effect on the utilization of citrate.
Postischemic hemodynamics and recovery of renal adenosine triphosphate
Authors: Gaudio K. M. , Stromski M. , Thulin G. , Ardito T. , Kashgarian M. , Siegel N. J.
Published: December 2017

Renal vasoconstriction is an important pathophysiological component of an ischemic acute renal injury. The postischemic infusion of ATP-MgCl2 enhances recovery of glomerular and tubular function, accelerates regeneration of sublethally injured tubular cells, and augments resynthesis of cellular nucleotides. Since both ATP and MgCl2 are vasoactive compounds, postischemic enhancement of renal blood flow (RBF) by a pharmacological agent, dopamine, was examined to study the possible contribution of vasodilation. At 2 h, the infusion of dopamine resulted in RBF (1.70 +/- 0.09 ml X min-1 X 100 g body wt-1 X kidney-1) and inulin clearance (CIn, 400 +/- 44 microliter X min-1 X 100 g body wt-1) similar to rats treated with ATP-MgCl2 (1.73 +/- 0.27 RBF, 404 +/- 38 CIn) and significantly (P less than 0.01) greater than saline-treated rats (0.80 +/- 0.04 RBF, 78 +/- 19 CIn; P less than 0.01). However, by 24 h CIn in dopamine animals had not continued to improve (460 +/- 25 microliter X min-1 X 100 g body wt-1) and was similar to normal saline rats (388 +/- 40). In contrast, CIn in ATP-MgCl2 animals showed sustained recovery (676 +/- 28 microliter X min-1 X 100 g body wt-1, P less than 0.01). These differences resulted from improved integrity of tubular epithelium as reflected by decreased cell swelling and necrosis. Moreover, the recovery of renal ATP levels, as assessed by 31P nuclear magnetic resonance, in animals given saline (63 +/- 3%) or dopamine (66 +/- 5%) was slow and incomplete by 120 min after ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of protein on glomerular filtration rate and prostanoid synthesis in normal and uremic rats
Authors: Levine M. M. , Kirschenbaum M. A. , Chaudhari A. , Wong M. W. , Bricker N. S.
Published: December 2017

Normal and uremic conscious rats that had been maintained on a low-protein diet were given oral protein or carbohydrate loads, and clearance studies were performed. Both the normal and uremic animals demonstrated a approximately 30% increase in glomerular filtration rate (GFR) in response to the protein bolus, but no significant increase in GFR was seen following the carbohydrate bolus. Similar studies were performed in uremic rats on a standard protein diet. The changes in GFR that were seen after an albumin bolus were similar but not as pronounced as those noted in the animals on the low-protein diet. Pretreatment with either aspirin or meclofenamate, cyclooxygenase inhibitors, completely blocked the protein-induced rise in GFR. The rats of glomerular production of prostaglandin (PG) E2 and 6-keto-PGF1 alpha (a stable metabolite of prostacyclin, PGI2) were determined by radioimmunoassay in a similar group of normal rats. The synthetic rates of PGE2 and 6-keto-PGF1 alpha following the protein bolus were 40 and 52% greater, respectively, than those observed following the carbohydrate load (P less than 0.005). Aspirin decreased glomerular prostanoid production in protein-treated animals by greater than 60%. Thus it appears that in the setting of protein restriction, the percent increase in GFR following a protein load is similar in both the normal and uremic rats, the increase in GFR in uremic rats is attenuated when animals were allowed to ingest a normal protein diet prior to study, and the increase in GFR seen in response to a protein load may be related to an increase in the synthesis of one or more vasodilatory glomerular prostanoids.
Relationships between calcium and chloride transport in frog skin glands
Authors: Ziyadeh F. N. , Kelepouris E. , Agus Z. S.
Published: December 2017

Frog skin gland, a furosemide-sensitive Cl(-)-secreting epithelium, exhibits Cl(-)-dependent Ca2+ secretion in response to stimulation by beta-adrenergic agonists. In this study, we further explored the relationships between Cl- and Ca2+ secretion in frog skin using 45Ca fluxes and short-circulating technique. On addition of isoproterenol (ISO) or 8-(p-chlorophenylthio)-cAMP, a significant positive correlation was demonstrated between Ca2+ secretion and Cl- secretion. Because Cl- transport in other Cl(-)-transporting epithelia may be modulated by prostaglandins or by changes in cytosolic Ca2+ activity, in addition to modulation by cAMP, we also examined the effects of prostaglandins (PG)E2 and F2 alpha, indomethacin (INDO), and the calcium ionophore A23187. Treatment with PGE2, PGF2 alpha, or A23187 at a dose of 10(-5) M resulted in marked stimulation in the amiloride-resistant short-circuit current, a reflection of Cl- secretion. This current was inhibited by furosemide addition or removal of Cl- from the bathing medium. However, and in contrast to stimulation with ISO or cAMP, PGE2, PGF2 alpha, and A23187 failed to induce Ca2+ secretion. In addition, the stimulation of Cl- secretion by A23187 was abolished by INDO (10(-6) M) pretreatment. Thus frog skin glands secrete Cl- via two mechanisms: one mediated by beta-adrenergic-cAMP stimulation and the other by activation of prostaglandin metabolism induced by changes in cytosolic Ca2+. Only the former pathway is associated with Ca2+ secretion. Furthermore, to account for the Cl- dependence of Ca2+ secretion, we postulate the existence of a Ca2+-Cl- cotransport system stimulated by cAMP.
Calcium and renal adaptation to a phosphate load in the thyroparathyroidectomized rat
Authors: Cheng L. , Dersch C. , Kraus E. , Sacktor B.
Published: December 2017

Infusion of phosphate into thyroparathyroidectomized rats on a normal phosphorus diet caused a decrease in net phosphate reabsorption, even though the plasma concentration of phosphate continued to rise. This response was expressed at the level of the proximal tubule brush-border membrane and was coincident with a decrease in sodium-dependent phosphate uptake in membrane vesicles. Kinetic experiments indicated that the increased phosphate load caused a decrease in the Vmax of the membrane uptake system with no change in the apparent Km for phosphate. The infusion of phosphate resulted in a lowered plasma calcium concentration, and it was previously hypothesized that the inhibition of maximal phosphate reabsorption was mediated by the hypocalcemia. When the fall in plasma calcium was prevented by the simultaneous infusions of calcium and phosphate, the reduction in maximal phosphate reabsorption was blunted; however, the phosphate infusion-induced inhibition of brush-border membrane vesicle phosphate uptake was still evident. Thus a major discrepancy was found to the general concept that renal phosphate reabsorption in vivo correlated positively with sodium-dependent phosphate uptake activity in proximal tubule brush-border membrane vesicles. Several possible explanations to account for this anomaly were discussed. It was also found that calcium infusion into saline-infused thyroparathyroidectomized rats slightly increased maximal phosphate reabsorption but did not affect phosphate uptake in the membrane vesicles.
Effects of parathyroid hormone and urinary phosphate on collecting duct hydrogen secretion
Authors: Mercier O. , Bichara M. , Paillard M. , Prigent A.
Published: December 2017

Urine-minus-blood PCO2 (U - B PCO2) during alkaline diuresis (urinary pH greater than 7.8) was determined in paired experiments using bicarbonate-loaded rats to assess the effects of parathyroid hormone (PTH) and urinary phosphate concentration [( Pi]u) on collecting duct H+ secretion. U-B PCO2 was higher for any value of urinary bicarbonate concentration ([HCO3]u) in the presence of PTH [intact rats and thyroparathyroidectomized (TPTX) PTH-infused rats] than in its absence (calcium-infused intact rats and TPTX rats). However, when [Pi]u was maintained constant by prior phosphate infusion, PTH administration in TPTX rats failed to elevate U-B PCO2. When PTH was infused in TPTX rats to maintain constant the plasma PTH level, subsequent phosphate infusion increased [Pi]u and elevated U-B PCO2 for any value of [HCO3]u. Moreover, when the data were pooled, there was a positive linear relationship between U-B PCO2 factored for [HCO3]u and [Pi]u (P less than 0.001). In all experiments, other factors that may affect U-B PCO2, such as plasma acid-base status, urinary osmolality, and extracellular fluid volume, did not vary. We conclude that PTH stimulates collecting duct H+ secretion indirectly via the increase in [Pi]u.
Release of atrial natriuretic factor. Effects of repetitive stretch and temperature
Authors: Bilder G. E. , Schofield T. L. , Blaine E. H.
Published: December 2017

The effect of continuous and repetitive mechanical stretch on release of immunoreactive atrial natriuretic factor (IR-ANF) was studied in isolated rat atria distended by inflation of miniature balloon catheters. After 10 min incubation, the concentration of IR-ANF in the medium increased in proportion to the degree of continuous atrial stretch. Repetitive atrial expansion induced a rate dependent increase in release of IR-ANF which at the highest rate tested (89 inflations/min) was sixfold greater than that observed with continuous maximal expansion. Comparison of the amount of IR-ANF released from the right or left atrium separately revealed that during continuous and repetitive stretch, both atria contribute equally to the total amount of release IR-ANF. A reduction of bath temperature (37 degrees to 21.5 degrees C) decreased both basal- and stretch-induced IR-ANF release approximately 85%. It was concluded that release of atrial natriuretic factor is temperature-dependent and induced by both the extent and rate of atrial stretch.
Effect of serotonin on prostaglandin synthesis in rat cultured mesangial cells
Authors: Knauss T. , Abboud H. E.
Published: December 2017

Serotonin (5-hydroxytryptamine) (5-HT) is a potent vasoactive amine that reduces renal blood flow and glomerular filtration rate. Vasodilator prostaglandins (PGs) modulate the effects of several vasoconstrictors on the renal circulation. Since mesangial cells are smooth muscle-like cells that may regulate glomerular hemodynamics, we studied the effect of 5-HT on PGs synthesis in rat cultured mesangial cells. 5-HT (10(-6)-10(-3) M) resulted in progressive stimulation of prostaglandin E2 (PGE2) synthesis. Significant stimulation in response to 10(-4) M 5-HT started after 2 min of incubation and progressively increased for at least 30 min. This effect was structurally specific for the 5-HT receptor since indole-containing precursors and metabolites of 5-HT as well as the aminergic compounds, adenosine, and dopamine were without effect. Moreover, 5-HT receptor antagonists, but not histaminergic or beta-adrenergic antagonists, abolished 5-HT-stimulated PGE2 synthesis. 5-HT also stimulated prostacyclin (measured as 6-ketoprostaglandin F1 alpha) but not thromboxane synthesis in the same cell cultures. 5-HT-stimulated PGE2 synthesis was not affected by extracellular calcium depletion but was abolished by preincubating the cells with the intracellular calcium antagonist 8-(N,N-diethylamine)-octyl-3,4-5 trimethoxybenzoate (10(-5) M). These studies show that 5-HT stimulates PGE2 and prostacyclin (PGI2) synthesis in mesangial cells via a mechanism dependent on intracellular calcium. These vasodilator PGs may modulate the effect of 5-HT on renal and specifically glomerular hemodynamics.