摘要:

The purpose of this study was to define individual nephron function and salt and fluid reabsorption in the term pregnant rat utilizing standard micropuncture techniques. The studies were performed at the time of maximal sodium retention and when extracellular fluid volume was significantly increased. During micropuncture in 7 pregnant and 9 non-pregnant rats, we found no difference, respectively, in GFR 1.04 + 0.06 vs. 1.13 ± 0.06 ml/min/kidney or nephron GFR 35 ± 0.9 vs. 33 ± 1 ml/min. Fractional and absolute Na reabsorption was also not significantly different in the proximal tubule or the loop of Henle. Along the distal tubule, fractional reabsorption was higher in pregnancy, 71 + 3 vs. 62 + 4 but not statistically different, 0.05 < p < 0.10. Beyond the late distal tubule absolute delivery and reabsorption were greater in the nonpregnant rats. Distal nephron potassium secretion was similar in both groups. In anesthetized rats during clearance studies but without surgery for micropuncture, GFR in the pregnant group was significantly higher than the nonpregnant rats, 1.65 + 0.06 vs. 1.28 + 1.10ml/min/kidneys as was tubular reabsorption of sodium. We conclude that pregnant rats exhibit glomerular tubular balance and that potassium handling along the superficial nephron is unaffected by pregnancy. The sodium retention of pregnancy appears to occur because of the failure of inhibition of tubular sodium reabsorption, a response which is normally expected when extracellular volume is expand

ISSN:1420-4096    

DOI:10.1159/000172833

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The effects of medium K+ concentration on the tissue uptake of p-aminohip-purate (PAH) were investigated in rat kidney cortex slices. K+ concentration in the incubation medium was changed in the absence of Na+. Increase in K+ concentration up to 145 mM revealed an augmenting effect on PAH uptake when tissue water content was controlled at about 72% by elevating medium osmolarity with mannitol. The K+-induced enhancement of PAH uptake was almost completely abolished by the simultaneous presence of extremely high concentration of hippurate. Anoxia reduced this augmenting effect. Pyruvate added to the medium scarcely affected this augmenting effect. The uptake rate during the initial 10-min incubation increased linearly in proportion to the increase in log [K]o /[K]i. The results suggest that high medium K+ concentration stimulates PAH transport by a carrier-mediated process which is dependent on oxidative metabolism. However, the mode of action of K+ on PAH uptake seems to be different from that of Na+. It seems likely that K+ exerts its effect on PAH transport by the alteration of the peritubular membrane potential.

ISSN:1420-4096    

DOI:10.1159/000172834

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Accumulation of p-aminohippurate (PAH) by rat kidney fragments incubating in vitro is enhanced as medium pH rises from 7.4 toward 7.8. Since medium pH increases from 7.4 to 7.8 over a 90-min period in the presence of acetate, we were unsure whether acetate had any direct stimulatory effect on transport. Rat renal fragments incubating in acetate showed no enhanced PAH accumulation at 30 and 60 min when medium pH was less than 7.6 but did increase approximately 25% after 90 min when pH approached 7.8. By a number of different procedures, we consistently found that when medium pH was not allowed to rise, acetate did not stimulate PAH accumulation. We conclude that at an initial pH of 7.4, acetate stimulation of PAH uptake by rat kidney fragments during the course of a 90-min incubation can be explained almost entirely by a rise in pH to a more optimal range for transport. In contrast, stimulation of PAH accumulation by lactate and pyruvate cannot be explained solely by changes in medium pH.

ISSN:1420-4096    

DOI:10.1159/000172835

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The renal clearance of inulin (Clin), 14C-creatinine (Cl14C.cr) and endogenous creatinine (Clcr) were measured in 6 healthy subjects before and after a single intravenous bolus of cimetidine (5 mg/kg). The initial Cli4C.cr/Clin ratio (mean ± SD) was 1.68 ± 0.17; this fell to a nadir of 1.35 ± 0.18 soon after cimetidine was infused and rose again as the drug was excreted. This is the first cationic drug to show substantial inhibition of tubular secretion of creatinine in huma

ISSN:1420-4096    

DOI:10.1159/000172836

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The effect of bradykinin (BK) on renal function was examined in anesthetized dogs with or without treatment with either indomethacin or propranolol. Renal arterial infusion of BK (3 μg/min) in control dogs produced a sustained increase in urine flow rate (V), sodium excretion (UNaV), potassium excretion (UKV), and renal plasma flow (RPF) without a consistent change in glomerular filtration rate (GFR) or renin secretion rate (RSR). This increase in salt and water excretion and in RPF could not be blocked with indomethacin (5 mg/kg, followed by 2.1–3.2 mg/kg/h, i.v.). UNaV was 20.8 ± 7.4 and 123.3 ± 22.3 μEq/min (mean ± SEM values) before and after 140 min of infusion of BK (p < 0.005), respectively. Beta-receptor blockade with propranolol (5 mg/kg, followed by 2.8–3.4 mg/kg/h, i.v.) did not prevent the BK-induced rise in salt and water excretion, or in RPF. UNaV was 26.0 ± 9.7 and 96.4 ± 21.5 μEq/min before and after 140 min of infusion of BK (p < 0.005), respectively. The data suggest that the effects of BK on renal handling of salt and water and on RPF are not mediated by either prostaglandins or bet

ISSN:1420-4096    

DOI:10.1159/000172837

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Renal phosphate (Pi) wastage following 7 days of starvation was investigated in normal rats (HI-P) and others previously stabilized on a low phosphorus (LO-P) diet. In LO-P animals, Pi excretion increased after starvation, but was significantly less than in starved HI-P rats. After thyroparathyroidectomy, the increase in Pi excretion after parathyroid hormone (PTH) was significantly greater in nonacidotic starved HI-P rats than in LO-P animals. However, PTH elicited a 31-fold increase in Pi excretion in both of these groups. Starved LO-P and HI-P rats responded equivalently to dibutyryl cyclic AMP. The renal response to phosphate depletion normally promotes Pi conservation, but is attenuated markedly by 7 days of subsequent starvation. This results from at least partial restoration of phosphaturic responsiveness to PTH during starvation.

ISSN:1420-4096    

DOI:10.1159/000172838

出版商:S. Karger AG    

年代:1982

数据来源: Karger