Possible mechanism of the inhibitory effect of ouabain on renin secretion from rat renal cortical slices.

Abstract

The effects of ouabain on renin secretion by rat renal cortical slices were studied. Renin secretion was inhibited by 10-3 M ouabain in the presence of free Ca (10-4 to 2.6 .times. 10-3 M). Inhibition was blocked at Ca < 10-8 M. The effect of free Ca on ouabain-inhibition was independent of the presence of EGTA [ethylene glycol-bis(.beta.-amino ethyl ether)N,N,N''-tetracetic acid], completely reversible, and unrelated to passive leakage of renin from non-viable cells, as assessed by simultaneous release of lactate dehydrogenase activity (LDH). Apparently due to inhibition of Na, K-ATPase by ouabain, intracellular Na increases in the renin-secreting juxtaglomerular cells, intracellular Ca increases, via an Na-Ca exchange mechanism, and Ca accumulation, in some unknown manner, inhibits renin secretion.