The proposed research includes an investigation of the regulatory effects of divalent metal cations on the generation of energy in cardiac mitochondrial systems. Also, the regulation of the mitochondrial alpha-ketoacid oxidases will be investigated with respect to the effects of fatty acids, adenine and pyridine nucleotides and coenzyme A derivatives. The effects of alterations in tissue GTP/GDP ratios will be investigated with respect to possible regulatory effects on the catecholamine response and other enzymatic systems involved in energy production and utilization. Bibliographic references: Schuster, S.M. and Olson M.S. Studies of the Energy-Dependent Uptake of Divalent Metal Ions by Beef Heart Mitochondria, J. Biol. Chem. 249, 7151-7158, 1974; Schuster, S.M. and Olson M.S. The Regulation of Pyruvate Dehydrogenase in Isolated Beef Heart Mitochondria: The Role of Calcium, Magnesium and Permeant Anions, J. Biol. Chem. 249, 7159-7165, 1974.