Calmodulin antagonism and inhibition of erythrocyte plasma membrane Ca + -pump by nifedipine, a calcium channel blocker

Abstract

Nifedipine, a 1,4-dihydropyridine Ca2+ -channel blocker inhibits calmodulin-stimulated activity of erythrocyte plasma membrane (Ca2+ + Mg2+) -ATPase. Its inhibition of the basal activity of the enzyme increases on pre-incubation with membranes. The maximum velocity, affinity for ATP and Ca 2+ -sensitivity of pump are reduced by micromolar amounts of the antihypertensive drug. These results suggest that 1,4-dihydropyridines may interact with calcium-binding proteins and calcium-dependent enzymes at their calcium-binding sites.