POSSIBLE MECHANISM OF THE INHIBITORY EFFECT OF OUABAIN ON RENIN SECRETION FROM RAT RENAL CORTICAL SLICES

1. The effects of ouabain on renin secretion by rat renal cortical slices were studied. 2. Renin secretion was inhibited by 10(‐3) M‐ouabain in the presence of free Ca (10(‐4) to 2.6 x 10(‐3) M). Inhibition was blocked at Ca less than 10(‐8) M. 3. The effect of free Ca on ouabain‐inhibition was shown to be independent of the presence of EGTA, completely reversible, and unrelated to passive leakage of renin from non‐viable cells, as assessed by simultaneous release of lactate dehydrogenase activity (LDH). 4. It is proposed that, as a result of inhibition of Na, K‐ATPase by ouabain, (a) intracellular Na increases in the renin‐secreting juxtaglomerular cells, (b) intracellular Ca increases, via an Na‐Ca exchange mechanism, and (c) that Ca accumulation, in some unknown manner, inhibits renin secretion. © 1979 The Physiological Society