Coenzyme Q10 supplementation and recovery from ischemia in senescent rat myocardium

Many studies have suggested that parenteral administration of coenzyme Q(10) (Q(10)) protects the myocardium of young experimental animals from post-ischemic reperfusion injury. Although parenteral administration, in contrast to per os supplementation, seems to elevate coenzyme Q concentrations in heart tissue, it is not suitable for prophylactic use. In addition, the incidence of ischemic events is greatest in older age. We studied the effect of Q(10) supplementation on myocardial postischemic recovery in 18-month-old Wistar rats. The treated group (n=9) received 10 mg/kg/day of Q(10) for 8 weeks in their chow while the normal chow of the control group (n=9) contained less than 0.5 mg/kg/day of Q(10). The treatment clearly elevated plasma Q(10) concentration (286 +/- 25 mu mol/l and 48 +/- 30 mu mol/l, treated and controls, respectively, p < 0.0001) but neither Q(9) nor Q(10) concentrations in heart tissue were affected by the supplementation. The isolated perfused hearts were subjected to 20 minutes of ischemia and 30 minutes of reperfusion. The preischemic values of developed pressure (DP) but not contractility (+DP/Delta t) and relaxation (-DP/Delta t) were improved by Q(10) supplementation (p = 0.034, p = 0.057 and p = 0.13, respectively) while in postischemic recovery no differences were observed between the groups (p > 0.05 at all time points). Also, in myocardial flow, myocardial oxygen consumption (MVO2) and myocardial aerobic efficiency (DP/MVO2) the groups did not differ at any time points. Although dietary Q(10) supplementation clearly elevated plasma Q(10) concentrations in senescent rats, the coenzyme Q contents in heart tissue and myocardial recovery from ischemia were not affected. However, it is possible that the site of action for the reported beneficial effects of Q(10) is in the coronary endothelium rather than myocardium itself.