[Electron-cytochemical and morphometric study of the activity of several enzymes in thyrocyte metochondria during malignant degeneration]

Cytochrome oxidase and succinic dehydrogenase activities were studied in the mitochondria of rat thyroid cell during experimental malignization by means of the electron-cytochemical and morphometric methods. The activity of these enzymes in the mitochondria changed depending on the stage of malignization: at the early stages it approached the normal activity, and at the later stages (precancer)--it decreased and approached the mitochondrial activity of cancer cells. A sharp decrease in the activity of the enzymes under study in the morphologically changed mitochondria of cancer cells may characterize their qualitative changes.