Effects of Prostaglandins E1 and F1α on the Heartlung Preparation of the Dog

1. Using the heart-lung preparation of the dog, the cardiac action of PGE1 and PGF1α were studied. Injection of PGE1 into the left atrium resulted in a positive inotropic effect and an increase in the coronary flow. The positive inotropic effect was especially prominent in the failing heart. Heart rate remained unchanged. There was no tendency toward tachyphylaxis in the action of PGE1. 2. In view of the very slight increase in the oxygen consumption observed after PGE1 (average 5%), the increase in the coronary flow produced by PGE1 (average 21%) was taken to represent a direct dilator effect of this compound on the coronary vasculature. 3. When injected into the venous-supply tubing, fifty to eighty times as high a dose of PGE1 was necessary to produce the coronary flow increase of the same magnitude as when injected into the left atrium. Thus, it was concluded that 98-99% of this compound was removed from the circulation during a single passage through the lung. 4. In the heart-lung preparation of the dog, the action of PGF1α was quite feeble, although the effects produced by large doses of this compound were not essentially different from those produced by PGE1.