Extracellular strontium substitutes for calcium in in vitro renin secretion

It has been shown previously that ouabain, vanadate, angiotensin II and 0 and 60 mM KCl media have Ca-dependent inhibitory effects on renin secretory rates of rat renal cortical slices. In the present experiments, replacing extracellular CaCl2 with SrCl2 did not impair the inhibitory effects on renin secretion in this preparation. Moreover, methoxyverapamil antagonized the inhibitory effect of K-depolarization. The inhibitory effects and methoxyverapamil-induced antagonism of the inhibitory effect of K-depolarization, suggest that increased intracellular Sr++ can lead to inhibition of renin secretion, perhaps directly or perhaps by causing the release or mobilization of Ca++ from intracellular sites of binding or sequestration. These results add to the growing evidence that Ca++ plays an inhibitory second messenger role in the renin secretory process.