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 inliibits calmodulin-stimulated activity of erytlirocyte plasma membrane (Ca 2 + + 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 calciumbinding sites.