摘要:

The excretion of potassium and the reabsorption of sodium were studied in isolated perfused kidneys of adrenalectomized rats following the administration of aldosterone. Aldosterone (10-7M) produced a rapid increase in fractional excretion of potassium, without affecting glomerular filtration rate, urine flow rate or sodium reabsorption. Spironolactone (10-4M) completely abolished the kaliuretic effect of aldosterone, while actinomycin D had no inhibitory effect. In the absence of exogenous metabolic substrate, enhancement of potassium excretion was not seen following aldosterone. With either glucose, pyruvate, lactate or α-ketoglutarate in the perfusion medium, the kaliuretic effect of aldosterone was restored. The results confirm the direct action of aldosterone on renal potassium excretion and its dependency upon the availability of specific metabolic substrates

ISSN:1420-4096    

DOI:10.1159/000172686

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The influence of glucose and substrates on sodium transport (TNa) and glucose transport (Tg) was studied in isolated rat kidneys perfused according to Bowman’s technique. Glucose (0–8 g/l) was added to the perfusion fluid in the presence or absence of substrates: i.e. 2·10-3M pyruvate, 2·10-3M lactate, 5.10-3M glutamic acid and 1·10-3M oxaloacetic acid. When glucose was used at different concentrations in the perfusate, a correlation was found between Tg and TNa (p < 0.001); when substrates were added, lactate was found to be the only substrate able to improve TNa significantly without affecting Tg. Fractional sodium reabsorption reached 98.54% when lactate and glucose (2 g/l) were present in the perfusion medium. The data suggest the existence of a link between TNa and Tg and the possibility of some dissociation betwee

ISSN:1420-4096    

DOI:10.1159/000172687

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Using taurine as a model substrate, β-amino acid transport in isolated rat renal cortical tubule segments as studied. Heterogeneity of taurine accumulation was found in tubule segments and has previously been measured in renal cortex slices. In contrast to studies in cortical slices, initial rate kinetics could also be determined, and demonstrated uptake by two systems. Efflux of taurine from tubule cells was measured and showed 50% remaining in tubule segments after 30 min incubation in taurine-free medium. Concentrative uptake was prevented by NaCN and iodoacetate. Incubation with other β-amino acids resulted in decreased taurine accumulation. An important although unexpected finding was decreased taurine uptake by isolated tubules in the presence of Krebs-Ringer phosphate and Tris-HCl buffer as compared to Krebs-Ringer bicarbonate buffer. Isolated tubule preparations provide a rapid means of assessing β-amino acid transport including initial rate kinetics. However, when using tubules to study uptake, the buffer medium may play a critical ro

ISSN:1420-4096    

DOI:10.1159/000172688

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The effects of methylguanidine (MG) were studied in proximal and distal tubules of the cortical nephrons of the rat kidney by the aid of various micropuncture techniques. Methylguanidine (5 × 10-4M/kg intravenously, as a bolus) depressed fluid and sodium reabsorption without affecting GFR. In proximal convoluted tubules, intravenous MG did not significantly affect the rate of isotonic fluid reabsorption measured with the split oil droplet technique; whereas, when MG (1 mM/1) was applied both from the peritubular side and intratubularly, isotonic fluid reabsorption was slightly depressed (p < 0.05). In the distal tubule, intravenous MG depressed fluid and sodium reabsorption

ISSN:1420-4096    

DOI:10.1159/000172689

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Using the recollection micropuncture technique it was demonstrated that the intragastric administration of triamterene significantly reduced the fraction of filtered potassium remaining (from 27 to 17%) and enhanced the fraction of filtered sodium remaining (from 3.6 to 7.9%) at the end of the accessible distal tubule in 7 rats. Fractional delivery of water, sodium and potassium to the distal tubule was not significantly altered. Urinary potassium excretion was reduced (from 17 to 7%). Similar experiments in 6 control rats disclosed no significant changes in the foregoing variables. In these experiments the principal effect of triamterene in vivo was an inhibition of potassium secretion in the distal tubule. An ostensible inhibitory effect on sodium reabsorption in the distal tubule was not unequivocally established.

ISSN:1420-4096    

DOI:10.1159/000172690

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

To determine the prostaglandin dependent and independent effects of bradykinin in the kidney, bradykinin (5.0 µg/min) was infused in the left renal artery during water diuresis in 17 hypophysectomized dogs, 9 control and 8 treated with indomethacin for 3 days before the study. In the control studies, bradykinin increased renin secretion (p < 0.02), cortical and non-cortical plasma flow (p < 0.05), and sodium and potassium excretion (p < 0.0005), without a change in glomerular filtration rate and with a decrease in distal fractional tubular reabsorption of chloride (p < 0.0025). In the studies with indomethacin, bradykinin increased renin secretion by 260 U/min, a significant (p < 0.02) response. Whereas cortical plasma flow did not change, non-cortical plasma flow, and sodium and potassium excretion increased and distal fractional tubular reabsorption of chloride decreased as in the control studies. Infusion of bradykinin at a lower dose of 0.5 µg/min did not change renin secretion or cortical plasma flow (p < 0.05), but increased non-cortical plasma flow and sodium excretion (p < 0.05). The results suggest that bradykinin increases cortical plasma flow by stimulation of prostaglandin synthesis, but increases renin secretion, non-cortical plasma flow and sodium and potassium excretion by an action which does not require the mediation of prostaglandins. An increase in renal plasma flow, which was a constant feature of renal arterial infusion of bradykinin, best explains the decrease in distal fractional chloride reabsorption and the increase in the excretion of sodiu

ISSN:1420-4096    

DOI:10.1159/000172691

出版商:S. Karger AG    

年代:1979

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000172692

出版商:S. Karger AG    

年代:1979

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000172693

出版商:S. Karger AG    

年代:1979

数据来源: Karger