Stimulation of Na+,K+-ATPase of isolated smooth muscle membranes by the Ca2+ channel inhibitors, nimodipine and nitrendipine.

Nimodipine (0.015 to 1.5 microM) increased Na+, K+-ATPase activity by 70-120% in isolated smooth muscle membranes. At 0.015 microM, nitrendipine, but not nifedipine, verapamil or diltiazem, also activated this enzyme. Nimodipine stimulated this Na+, K+ATPase three times more than nitrendipine at 15 nM. Marked stimulation of Na+,K+-ATPase by nimodipine was seen in membranes from rat and guinea pig aorta and rat vas deferens, but not in membranes from guinea pig heart or brain. Although it is not known whether these results are applicable to intact cells, the results are consistent with the hypothesis that vasodilation produced by nimodipine and nitrendipine may be due not only to inhibition of Ca2+ entry but also to the stimulation of the Na+ pump.