Recovery of free ADP, P(i), and free energy of ATP hydrolysis in human skeletal muscle

We measured significant undershoots of the concentrations of free ADP ([ADP]) and P(i) ([P(i)]) and the free energy of ATP hydrolysis (ΔG(ATP)) below initial resting levels during recovery from severe ischemic exercise with ³¹p-nuclear magnetic resonance spectroscopy in 11 healthy sports students. Undershoots of the rate of oxidative phosphorylation would be predicted if the rate of oxidative phosphorylation would depend solely on free [ADP], [P(i)], or ΔG(ATP). However, undershoots of the rate of oxidative phosphorylation have not been reported in the literature. Furthermore, undershoots of the rate of oxidative phosphorylation are unlikely because there is evidence that a balance between ATP production and consumption cannot be achieved if an undershoot of the rate of oxidative phosphorylation actually occurs. Therefore, oxidative phosphorylation seems to depend not only on free [ADP], [P(i)], or ΔG(ATP). An explanation is that acidosis-related or other factors control oxidative phosphorylation additionally, at least under some conditions.