Myocardial biosynthesis of prostacyclin and the influence of cardiac loading and drugs.

Cardiac tissue from different parts of hearts from guinea pigs and rabbits have the capacity to rapidly synthesize prostacyclin (PGI2). Auricles show a higher PGI2-formation than ventricles. Addition of the endoperoxide PGH2 markedly enhanced the myocardial PGI2-biosynthesis. Furthermore many cardiotonic drugs induced a significant rise, but eicosanoids or cyclooxygenase inhibitors a marked reduction of the cardiac PGI2-formation. Acute pressure overload by graduated aortic stenosis, ischemia by coronary ligation or pacing with high frequency reduced the cardiac contractility. After aortic stenosis the myocardial PGI2-biosynthesis is lowered, but increased after coronary ligation or pacing. Under these conditions indomethacin, PGE1, iloprost, verapamil and trapidil markedly reduced the PGI2-biosynthesis and exert a protective effect in regard to cardiac damage. The results indicate that pathophysiological changes significantly influence the PGI2-biosynthesis of the heart. The drug induced inhibition of the myocardial PGI2-formation parallels a cardioprotective effect of these substances.