Abstract
The effects of catecholamines on the beating of rat heart cells in monolayer culture were examined. On adding 2×10-5M reserpine to the culture medium, the beating of heart cells stopped and as long as the cells were cultured in medium containing reserpine, beating did not resume to that observed before treatment with reserpine. When placed in a fresh medium without reserpine, some cells resumed beating after a lag period of 1 to 2 hr. Addition of 10-5M epinephrine or dopamine to the fresh medium reduced the lag period and the beating started within 5 to 20 min. Dopa had no effect on the beating. Propranolol, a β-adrenergic blocking agent, delayed the effect of norepinephrine. Acetylcholine (10-7-10-5M) or carbacol (10-5M) had no effect. From these results, it is suggested that catecholamines evoke the contraction of cultured heart cells, and that the rhythmical beat may be due to repeated cycles of depletion and replenishment of catecholamines.
