[Effect of metabolism on the electrical and mechanical activities of the frog atrium]

Due to glycolysis, anaerobic ATP supports normal electrical activity and allows only a reduced but sustained mechanical activity; however, frog myocardium metabolism is mainly aerobic dependent. Krebs cycle provides ATP for both mechanical and electrical acitivites even when glycolysis is inhibited. The close correlation between amplitude of contraction and metabolic state suggests that ATP is a limiting factor of mechanical activity even in normal conditions. Therefore it is necessary to use oxygen and to add pyruvate which partly compensate for the decrease of mechanical activity observed during the occurrence of hypodynamic state. Moreover equilibrating the oncotic pressure prevents hypodynamia and considerably improves the experimental conditions.