ELECTRON MICROSCOPIC DEMONSTRATION OF ENERGY PRODUCTION AND COUPLED RESPIRATION OF IN SITU MITOCHONDRIA

Respiratory-linked accumulation of Sr 2+ was applied to visualize mitochondrial energy production in unfixed slices of liver, kidney and heart muscle. The reaction was dependent on the function of the respiratory chain and energy coupling as was shown by the inhibitory effect of KCN and 2,4-dinitrophenol. The electron-dense granular or needle-like reaction product was localized in the inner compartment of the swollen mitochondria. Sr 2+ translocation was also utilized to detect the coupled oxidation of different respiratory substrates. The overwhelming majority of mitochondria showed, more or less, activity when malate was oxidized. In the kidney and heart muscle a few mitochondria, however, did not show succinate-supported Sr 2+ accumulation. This points to the possible differences in substrate utilization of mitochondria localized in the same cells. In the liver all mitochondria exhibited marked reaction with both substrates.