CA-DEPENDENCE OF THE INHIBITORY EFFECT OF K-DEPOLARIZATION ON RENIN SECRETION FROM RAT-KIDNEY SLICES

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 258  (2) , 300-312
Abstract
Renin secretion of rat kidney slices was studied as a function of extracellular K concentration. Independently of osmolality and extracellular Na and Cl concentrations, increasing K inhibited secretory rate in a concentration-dependent manner. At 60 mM K, rates were only a few percent (1.6 .+-. 0.8 and 3.5 .+-. 0.5%, depending on Na and/or osmolality) of the rate measured at 4 mM K. Lowering extracellular Ca concentration from 2.65 .times. 10-3-< 10-8 M stimulated secretion and abolished the inhibitory effect of 60 mM K; these effects were reversible. Methoxyverapamil and verapamil antagonized the inhibitory effect of 60 mM K in concentration-dependent manners; methoxyverapamil was the more potent. Lowering Ca from 3.0 to 0.25 mM potentiated the antagonistic effects of both drugs. Depolarization of juxtaglomerular cells evidently opens voltage-sensitive Ca channels, and the influx of Ca mediates the inhibitory effect of depolarization on renin secretion. Intracellular Ca evidently plays an inhibitory coupling role in the control of renin secretion.

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