Increased bumber of bata-adrenoceptors in cultured heart cells after propranolol withdrawal.

Abstract

We have studied the effects of propranolol on the number and function of beta-adrenoceptors of cultured heart cells from mice. After 24 hrs in culture, heart cells were incubated for 48 hrs with either standard medium or medium containing propranolol. After a washing period of 30 min, beta-adrenoceptors were measured with a receptor binding assay. The dissociation constant (Kd) did not differ between control and cultured heart cells pretreated with propranolol. By contrast, the maximum number of binding sites (Bmax) was 2.5 times higher in propranolol-pretreated than control cultured heart cells. The increase in the rate of beating and the elevation of cyclic AMP content induced by 10(-5) M isoproterenol were significantly higher for cultured cells pretreated with propranolol than for control cells. These results indicate a correlation between an increased number of beta-adrenoceptors and increased physiological responses of cultured heart cells after propranolol withdrawal.