This study is aimed at elucidating some aspects of the metabolism of polyunsaturated fatty acids, hydroxy fatty acids, prostaglandins and leukotrienes in heart and liver. Special attention will be given to the Beta-oxidation of: (1) unsaturated fatty acids with cis or trans double bonds extending from even-numbered carbons as well as from odd-numbered carbons, (2) D-hydroxy fatty acids with the hydroxyl group attached to odd-numbered carbons as for example in 5-hydroxy-6,8,11,13-eicosatetraenoic acid (5-HETE), and (3) prostaglandins. These studies will be performed with isolated Beta-oxidation enzymes and with mitochondria. The tissue distribution and physiological function of 3-hydroxyacyl-CoA epimerase will be studied and this enzyme will be purified and characterized. The possible inhibition of fatty acid oxidation by D-3-hydorxy fatty acids, leukotrienes and prostaglandins will be evaluated in rat heart and liver mitochondria. The results of this study are expected to contribute to a better understanding of fatty acid oxidation in normal and diseased tissue, especially in patients afflicted with Reye's syndrome.