Effects of coenzyme Q10 on recovery of hypoxia-induced changes in ATP and creatine phosphate contents of sinoatrial nodal cells of the rabbit's heart after reoxygenation.

We have studied the effects of reoxygenation on hypoxia-induced changes in contents of high energy phosphate compounds in pacemaker cells of nodal tissues excised from the rabbit heart, and effects of coenzyme Q10 on the electrical activity and metabolite contents in the tissue exposed to hypoxia and then reoxygenated. The contents of ATP and creatine phosphate (CP) in the sinoatrial node tissue were markedly reduced within 15-30 min after exposure to hypoxic Tyrode's solution. Reoxygenation produced almost complete recovery of the tissue ATP, but not of CP. After 60-120 min of hypoxia, the tissue ATP and CP decreased to about 60-30% of the initial value, but were not recovered by reoxygenation. Coenzyme Q10 (CoQ) at concentrations of 10(-6)-10(-5) g/ml did not produce changes in action potential parameters in the normal Tyrode's solution. CoQ (10(-5) g/ml) did not prevent the decreases in tissular ATP and CP in the initial period of hypoxia (30-60 min), but the ATP content at 120 min of hypoxia in the presence of CoQ was higher than the control. CoQ promoted recovery of tissular ATP after reoxygenation. Our results provide direct evidence that generation of action potentials in the sinoatrial nodal cells can be maintained by a small amount of ATP produced by the anaerobic glycolytic pathway. The present results suggest that exogenous CoQ would facilitate resynthesis of ATP in the functionally impaired mitochondria.