THE EFFECT OF DIPYRIDAMOLE ON THE METABOLISM OF CARDIAC MUSCLE

¹ Department of Pharmacology, Wyeth Laboratories Inc., Radnor, Pennsylvania

The relationship between the metabolic and inotropic effect of dipyridamole on in vitro preparations of cat papillary and left atrial muscles was investigated. The oxygen consumption, contractility, glycogen content and energy-rich phosphate levels were used as parameters. They were measured by techniques previously described by Lee et at. (1960). Dipyridamole had no effect on the oxygen consumption of resting muscle. However, it increased both the contractility and oxygen consumption of electrically stimulated muscle, an increase in contractility occurring before oxygen consumption changed. Dipyridamole did not increase the mechanical efficiency of fresh, contracting papillary muscle; however, it did cause an apparent increase with atrial muscle. Dipyridamole did not significantly change the tissue content of either glycogen or energy-rich phosphate compounds. Both pronethalol and reserpine pretreatment were found to block dipyridamole's inotropic effect. From the above data, it is concluded that the increase in oxygen consumption after dipyridamole is a consequence of the increased contractility and furthermore, based on the interaction with reserpine and pronethalol, that dipyridamole increases contractility through an adrenergic mechanism.