Canine coronary vascular and cardiac responses to the prostaglandins.

The actions of intracoronary prostaglandins (PG) E1 A1, and F2α on coronary vascular resistance and cardiac function were studied in anaesthetized, open-chest dogs. PGEi produced potent, direct, coronary vasodilatation in both the beating, fibrillating and arrested heart. PG vasodilatation was not associated with increase in coronary A-V oxygen difference or myocardial oxygen consumption, nor with the release of K+ into coronary venous blood. PGA1was a less potent coronary dilator and PGF2α did not significantly affect coronary resistance or LV function. PGE1 and A1 both increased myocardial contractile force, reduced ventricular end-diastolic length, and in larger doses decreased systemic pressure. At constant heart rate an initial increase in cardiac output and venous return was followed by a more sustained fall.