Effects of cardioactive drugs on the beating activity of myocardial cell cultures isolated from offspring of trained and untrained pregnant rats.

Primary cultures of beating myocardial cells were obtained from 5-d-old offspring of trained (T) and untrained (UT), pregnant, Sprague-Dawley rats. The myocardial cells from the T and UT groups were evaluated for their beating responses to three cardioactive drugs: verapamil (V), isoproterenol (ISO), and propranolol (PRO). The myocardial cell cultures from the UT group showed complete loss of beating when the calcium (Ca++) antagonist, V, was added to the cultures for 1 h or more; the T group was able to show some beating at comparable concentrations and durations of exposure with V. The beta agonist, ISO, markedly stimulated the beating rate of both the T and UT groups, but the beating rates were higher in the UT group at comparable concentrations and durations of exposure than with the T group. When the cultures were pretreated with the beta blocker, PRO, before treatment with ISO, a concentration inhibitory effect on the beating rate was observed in both groups. However, the T cultures were more sensitive to the inhibitory effects of PRO. These results demonstrate that primary cultures of rat myocardial cells isolated from the offspring of trained and untrained pregnant rats show differential beating responses to three well-known cardioactive drugs.