DNP‐induced dissipation of ATP in anoxic ventricular muscle

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Abstract
1. During aerobic incubation in 5 mM glucose medium, 10−5 M‐DNP reduced the action potential duration and amplitude and the developed tension of guinea‐pig ventricular muscle more rapidly and to a greater extent than anoxia.2. The DNP effect on electrical and mechanical activity was even more pronounced following prolonged anoxic incubation. Since the action potential duration and developed tension of anoxic ventricular muscle have previously been shown to be dependent on glycolytic ATP, and since the effects of DNP could not be duplicated with NaCN, it was concluded that DNP was exerting an effect in addition to its uncoupling of oxidative phosphorylation.3. Anoxic muscle was incubated with 10−4 M‐IAA or with 10−4 M‐IAA + 10−4 M‐DNP. The ATP content of IAA‐treated muscle was significantly lower than control but in the presence of both IAA and DNP there was a further reduction in ATP and an increased lactate production.4. Sodium azide (10−2 M), a potent inhibitor of mitochondrial ATPase, did not prevent the reduction of ATP in DNP‐treated anoxic muscle.5. Ouabain (10−7 M) partially prevented the rapid decline of action potential duration and developed tension of DNP‐treated anoxic muscle. In addition, the glycoside partially blocked the DNP‐induced break‐down of ATP and stimulation of lactate production.6. Oligomycin (10 μg/ml.) partially prevented the reduction in action potential duration and developed tension of DNP‐treated anoxic muscle.7. It was concluded that DNP induces an ‘energy leak’ by actively promoting the hydrolysis of an high energy glycolytic intermediate at least one step beyond the sites of ATPase inhibition by ouabain and oligomycin.