MYOCARDIAL AND CORONARY EFFECTS OF EXOGENOUS ARACHIDONIC-ACID ON THE ISOLATED AND PERFUSED HEART PREPARATION AND ITS METABOLISM IN THE HEART OF TROUT (ONCORHYNCHUS-MYKISS)

1. The effects of arachidonate (AA) on myocardial and coronary function, and the ability to metabolize AA have been explored for the first time in the heart of rainbow trout, Oncorhynchus mykiss. 2. On the isolated and perfused working heart exogenous AA (10(-7) and 10(-5) M) elicits a significant reduction of cardiac output and power output while heart rate is unaffected. 3. The negative inotropic effect is abolished in presence of 10(-5) M indomethacin. At the same AA concentration a pronounced increase in coronary resistance (175% change from baseline values) is apparent which is reduced but not abolished in the presence of 10(-5) M indomethacin. 4. C-14-arachidonate is metabolized by trout ventricle homogenate into PGs E2, F2alpha, D2, and in lesser amount into TXB2 and 6-keto-PGF1alpha. Ca-ionophore A23187 enhances the production of both PGE2 and PGF2alpha. The lipoxygenase products assayed as the hydroxy acids (HETEs) appear to be less actively synthesized than prostanoids.