Regulation of the pyruvate dehydrogenase activity in the isolated perfused heart of guinea-pigs.

The activity and the interconversion of the between the pyruvate after pyruvate should read: utilization in the perfused hearts and the pyruvate dehydrogenease complex has been measured in the isolated perfused working hearts of guinea-pigs. 1. The pyruvate dehydrogenase complex is transferred into the active form by high work, in anoxia, with 2,4-dinitrophenol and by perfusion without substrate. The rate of interconversion is faster in the perfused heart than in the homogenate. 2. The active form of the pyruvate dehydrogenase complex limits the pyruvate oxidation. There is a close correlation between the pyruvate utilization in the perfused hearts and the pyruvate dehydrogenase of the active form in the homogenates of the same hearts. 3. The "adenylate energy charge" of the cells is considered as the main regulating factor of the interconversion of the pyruvate dehydrogenase complex as seen in experiments with anoxia, dinitrophenol and high work. The inactivation of the pyruvate dehydrogenase complex by acetyl CoA can be overcome by decreasing ATP/ADP ratios.