Effects of dihydropyridine calcium antagonists on rabbit renal Na,K-ATPase activity in vitro.

Dihydropyridines are reported to have a stimulatory effect on vascular smooth muscle Na,K-ATPase activity in vitro. We studied the effects of the dihydropyridine calcium antagonists nimodipine, nitrendipine, nisoldipine, niludipine, nifedipine and felodipine (10(-5) M) on purified Na,K-ATPase isolated from rabbit kidney outer medulla. We were unable to detect an effect of the drugs on the enzyme activity, either under optimal or suboptimal substrate conditions. Likewise, Na,K-ATPase activity, partly inhibited by the addition of ouabain (10(-6) M), Ca2+ (10(-3) M) or arachidonic acid (4 x 10(-5) M), was not influenced by the dihydropyridines. The absence of a stimulatory effect of dihydropyridines on renal Na,K-ATPase is in agreement with the known diuretic and natriuretic effects of the drugs in normotensive and hypertensive men.