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  • 1
    ISSN: 1432-2013
    Keywords: Adrenalectomy ; Tubuloglomerular feedback ; Intratubular stop flow pressure ; Loop of Henle ; Diluting capacity ; Renal renin content ; Dexamethasone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The technique of orthograde tubular microperfusion has been used to test the functional integrity of tubuloglomerular feedback control in adrenalectomized rats. Kidneys of these animals display high renin contents, as well as an impairment of electrolyte transport in the loop of Henle, which was demonstrated by monitoring the electrical conductivity of fluid entering the distal tubule over a perfusion range of 10–50 nl/min. The calculated electrolyte concentration of the perfusion fluid leaving the loop of Henle was significantly higher in adrenalectomized rats than in controls. Intratubular stop flow pressure (SFP) during perfusion with a modified “endproximal” Ringer's solution was recorded continuously in early proximal segments at rates of 0–40 nl/min. Direct pressure transmission from perfused endproximal tubular segments to the pressure recording capillary was prevented by paraffin blockade of the intermediate proximal segment. An intact feedback response in each of the 32 tubules of the adrenalectomized rats studied was observed, which was reversible and could be demonstrated repetitively in individual tubules. Thus ΔSFP at 40 nl/min was −11.2±1.3 mm Hg in adx rats as compared to −8.1±1.3 in control rats. An increased freedback sensitivity was observed in dexamethasone treated adrenalectomized rats despite normal renal renin content. Here ΔSFP at 40 nl/min was −15±1.1. Thus, the feedback signal can be mediated in the apparent absence of adrenal steroid hormones and a high sensitivity of tubuloglomerular feedback control is not necessarily paralleled by high renin content of renal tissue.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Renin ; Angiotensin ; Electrolytes ; Kidney Slices ; Rat ; Renin ; Angiotensin ; Elektrolyte ; Nierenschnitte ; Ratte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Nierenschnitte von Wistarratten wurden in NaCl-Lösungen oder in Ringer-Bicarbonat(bzw. Phosphat-)-Puffern mit 0,1 g Glucose/l für 2 Std bei 37° C aerob inkubiert. 0,1 ml Medium wurde mit 1,9 ml Rinder-Reninsubstratlösung in Anwesenheit von Diisopropylfluorophosphat und EDTA bei pH 5,7 und 37° C für 2 Std inkubiert. Der Angiotensingehalt des Inkubates wurde im Blutdrucktest der Ratte bestimmt. In verschieden konzentrierten NaCl-Lösungen nimmt die Reninabgabe von 150–67 m Val/l (Na+) kontinuierlich ab. Auch in Ringer-Lösungen mit abnehmender NaCl-Konzentration und konstanter Konzentration der übrigen Elektrolyte findet sich zwischen 120 und 50 m Val/l (Na+) ein steiler Abfall der Reninabgabe. Bei Konstanterhaltung der Osmolarität durch zunehmenden Ersatz des NaCl durch Cholinchlorid oder Mannit vermindert sich die Steilheit der (Na+)-Abhängigkeit der Reninabgabe. Ersatz des NaCl im Bicarbonatpuffer durch verschiedene Konzentrationen von NaBr ergibt die gleichen Befunde wie mit NaCl. Bei vollständigem Ersatz des NaCl im Puffer durch verschiedene Konzentrationen von Chlolinchorid oder Mannit ist die Konzentrationsabhängigkeit der Reninabgabe weniger deutlich, bei Ersatz durch KCl nicht mehr signifikant. Die (Na+)-Abhängigkeit der Reninabgabe aus Nierenschnitten scheint nicht vom aeroben Stoffwechsel abhängig zu sein.
    Notes: Summary Rat kidney slices were incubated in saline solutions or in Ringer-bicarbonate (resp. phosphate-)-buffers containing 0.1 g/l glucose for 2 hrs at 37° C. Subsequently, 0.1 ml of the medium was incubated with 1.9 ml of ox renin-substrate solution, pH 5.7, for 2 hrs at 37° C in the presence of diisopropylfluorophosphate and EDTA. The angiotensin formed was measured by rat blood pressure assay. Renin release from kidney slices decreases markedly in NaCl-solutions between Na+-concentrations of 150 meq/l and 67 meq/l. Renin release decreases likewise in modified Ringer-solutions containing decreasing amounts of NaCl or NaBr (between 120 meq/l and 50 meq/l Na+), when the concentrations of other electrolytes are held constant. The (Na+)-dependence of renin release is less marked when the osmolarity of the medium is held constant by stepwise substitution of NaCl cholinchloride. Complete substitution of NaCl by different concentrations of cholin-chloride or mannitol diminishes the dependence of renin release on the osmolarity of the medium. Variation of KCl-concentration in the absence of NaCl does not influence renin release significantly. The (Na+)-dependence of renin release does not seem to depend on aerobic conditions.
    Type of Medium: Electronic Resource
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