Stimulation and suppression of renin release from incubations of rat renal cortex by factors affecting calcium flux.

Inhibition of renin secretion from incubations of rat kidney cortex by angiotensin II (AII), ouabain and K+ depletion, depended on the presence of external Ca2+. AII inhibition of isoprenaline-stimulated renin secretion was only partially dependent on external Ca2+. Ouabain and K+ depletion inhibited isoprenaline-stimulated renin release but only in the presence of external Ca2+. Since, in Ca2+-free medium, isoprenaline stimulated renin release when the Na+/K+-ATPase was blocked, isoprenaline probably does not act through the Na+/K+-ATPase. Lanthanum blocked the stimulation of renin release by isoprenaline. Ethylenediamine tetra-acetic acid (EDTA) and ethyleneglycol-bis-(beta-amino-ethyl ether) N,N'-tetra-acetic acid (EGTA) increased renin secretion to a similar degree in Ca2+- and Mg2+-free buffer. When Mg2+ was present the effect of EGTA, but not EDTA, was considerably reduced. Verapamil reduced the fall in basal renin secretion in normal but not Ca2+-free buffer. Verapamil did not block the inhibitory effects of AII or ouabain and did not alter the stimulation of renin secretion by isoprenaline. Bay K 8644 inhibited renin secretion from cortex incubated in medium containing 15 mM K+ and this was dependent on extracellular Ca2+. In normal buffer (5.9 mM K+) Bay K 8644 increased renin secretion.