Effect of calmodulin inhibitors on rat and guinea pig myocardial contractility.

Abstract

The effects of phenothiazine drugs with different affinities for calmodulin (trifluoperazine, frenolone, majeptile and aminazine) on the contractility of rat and guinea pig papillary muscles were studied. The phenothiazine-induced changes in the contraction-relaxation parameters were shown to correlate with the degree of calmodulin inhibition. These parameters are relaxation-onset index, relaxation index and terminal relaxation index in rats, and relaxation index and maximal developed tension in guinea pigs. An essential role of calmodulin in myocardium relaxation in both animal species is postulated.