Electron-cytochemical and morphometric investigation of enzyme activity in thyrocyte mitochondria during carcinogenesis

Activity of cytochrome oxidase and succinate dehydrogenase in the mitochondria of thyroid gland cells of rats was studied by electron-histochemical and morphometric methods during experimental carcinogenesis. The activity of these enzymes in the mitochondria was shown to vary depending on the stage of malignant transformation: In the early stages it was close to normal, but later (precancer) it fell sharply and approached the level observed in the mitochondria of cancer cells. A marked decrease in the activity of the enzymes studied in the morphologically altered mitochondria of cancer cells may be a qualitative characteristic of these cells.Electron Microscopy Room, N. K. Kol'tsov Institute of Developmental Biology, Academy of Sciences of the USSR. Laboratory of Electron Microscopy, Institute of Poliomyelitis and Virus Encephalitis, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 4, pp. 452–455, April, 1977.