[Effect of calmodulin inhibitors on the contraction and relaxation of the heart muscle].

The calmodulin inhibitor trifluoroperazine (5 microM) diminished the velocity of contraction and relaxation of the guinea-pig papillary muscle by 31 and 53%, respectively. Methophenazine showed approximately the same affinity to both calmodulin and trifluoroperazine and nearly 40-fold less affinity to troponin. Methophenazine (5 microM) did not change the contraction velocity and diminished the relaxation velocity ty 21%. It is suggested that calmodulin participates mainly in the control of myocardial relaxation.