Effects of Drugs on the Interaction of Calcium and Cardiac Muscle Memberane Fragments

ABSTRACT

The effect of drugs on calcium-binding to cardiac muscle membrane fragments and its turnover rate was studied. Ouabian, acetylcholine, isoproterenol and norepinephrine did not have any effect either on calcium-binding to membrane fragments or an washout ahnd release curves of previously bound calcium. Local anesthetics inhibited the calcium-binding. Tetracaine at concentrations of 1 and 10 mM inhibited the calcium-binding by 30% and 54%, respectively, while 10 mM lidocaine inhibited it by 17%. Propranolol, a well-known adrenergic beta-blocker, also inhibited calcium-binding at the external calcium concentration of 10(-3) M. This effect of propranolol may be attributed to its local anesthetic-like action, rather than to the adrenergic blocking effect.