[Some peculiarities of ATPase in tumor mitochondria]

The oxidative phosphorylation and ATPase activity (initial and stimulated by DNP and Mg2+) in tumor mitochondria were investigated. The intact mitochondria of Zajdela hepatoma, in contrast to liver mitochondria, exhibit the ATPase activity which is slightly stimulated by 2,4-dinitrophenol and is markedly activated by Mg2+. The mitochondria from transplantable solid tumors (adenocarcinoma 755, Iensen sarcoma, sarcoma 45) despite satisfactory morphological integrity under electron microscopy are biochemically less intact than the mitochondria of hepatoma. ATPase of these mitochondria is also slightly stimulated by 2,4-dinitrophenol and significantly by Mg2+. The ATPase activity of thymus mitochondria, the normal tissue with sufficiently high proliferative activity, corresponds to that of tumor mitochondria. The total amount of enzyme in mitochondria of tumors investigated and thymus is not lowered, since the ATPase activity in the presence of both DNP and Mg2+ corresponds to the ATPase activity of liver mitochondria. The Mg2+ ATPase activity of tumor mitochondria is not sensitive or is only partly sensitive to oligomycin. The data obtained are indicative of a high lability of the phosphorylating system in tumor and thymus mitochondria. A possibility of reorganization of the energy mechanism of tumor mitochondria and some normal tissues in connection with increased metabolism requiring high energy consumption, is discussed.