Effects of prostacyclin (PGI2) and adenosine (ASN) on total and regional blood flow of isolated, collateralized dog hearts

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Abstract
Dogs were subjected to chronic occlusion of the left circumflex and the right coronary artery by ameroid-type constrictors 4–5 weeks before the experiments. The hearts were isolated, fibrillated and perfused with blood (100 mmHg) from a support dog. Total and regional myocardial blood flow as well as peripheral coronary pressure (circumflex artery) were determined before and during infusion of PGI2 and ASN into the isolated hearts. Both drugs increased total and regional blood flow to all parts of the myocardium in a dose-dependent manner, PGI2 being 2–3 times more potent than ASN. The perfusion pressure for the collateral-dependent myocardium, the peripheral coronary pressure, decreased following high doses of both drugs. For PGI2 a dose level existed where total flow was increased, while peripheral coronary pressure remained unaffected. After termination of the infusion of PGI2, peripheral coronary pressure rose above predrug level with the total blood flow still being elevated. These findings indicate a PGI2-induced dilatation of collateral vessels. In general, the hemodynamic profile within the isolated hearts and the support dogs was characterized by the pronounced vasodilatory effects of PGI2 on arterioles. However, these effects did not deteriorate further the nonhomogenous blood flow distribution in the collateralized portions of the myocardium. The findings suggest that PGI2 is not a specific coronary vasodilator.