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Energy-linked Functions of Tightly Coupled Mitochondria Isolated from Ehrlich Ascites Tumor Cells¹

Department of Biochemistry, Faculty of Science, The Australian National University, Canberra, A. C. T., Australia

Tightly coupled mitochondria isolated from Ehrlich ascites tumor cells contain a latent adenosine triphosphatase (ATPase) that is stimulated by a range of dinitrophenol concentrations up to 0.5 mM. Maximal uncoupler-stimulated ATPase activity is approximately 60% of that found with rat liver mitochondria and is inhibited by oligomycin and by atractyloside.

Rapid rates of ATPase activity accompany the accumulation of Ca²⁺ by ascites tumor mitochondria in an adenosine triphosphate-supported system. In contrast to Ca²⁺, Mg²⁺ is unable to induce ATPase activity in intact mitochondria but can in sonically disrupted preparations. Prolonged incubation of the ascites mitochondria with Ca²⁺ does not lead to irreversible ATPase, swelling, or spontaneous release of the accumulated Ca²⁺, events typical of rat liver mitochondria.

¹ This study was supported by a grant from the Australian Capital Territory Cancer Society.

Received 3/29/73. Accepted 7/ 5/73.