ACTION OF DIPHENYLHYDANTOIN ON RHYTHMICITY AND CONTRACTILITY OF CULTURED EMBRYONIC HEART CELLS

¹ Department of Medicine, Maimonides Medical Center, and State University of New York, Downstate Medical Center, Brooklyn, New York

Chick embryonic heart cells were prepared by trypsin dissociation of embryos eight to nine days in ovo and were grown in a medium containing low potassium (less than 125 mEq/liter). After 24-hour cultivation, the cells were exposed to variable concentrations of diphenylhydantoin, and its effect on contraction rate and contractility of the heart cells was studied. A significant decrease in contraction rate (P <.05) was observed at concentrations of diphenylhydantoin of 25 µg/ml or higher when compared to control. At concentrations of 40 µg/ml or higher, the decrease in rate of contraction was consistently associated with a decrease in contractility of the heart cells. Diphenyihydantoin did not counteract the inotropic and chronotropic effects produced by 10^-8 to 10^-7 M digoxin nor prevent the toxic effects of 10^-8 M digoxin. However, diphenylhydantoin delayed the onset of digoxin-induced cellular arrhythmias.