Age-associated deterioration of arterial function may result from long-lasting oxidative stress. Since coenzyme Q (Q10) has been suggested to protect the vascular endothelium from free radical-induced damage, we investigated the effects of long-term dietary Q10 supplementation on arterial function in senescent Wistar rats. 2. At 16 months of age, 18 rats were divided into two groups. The control group was kept on a standard diet while the other group was supplemented with Q10 (10 mg kg(-1) day(-1)). In addition, nine rats (age 2 months) also ingesting a standard diet were used as the young control group. After 8 study weeks the responses of the mesenteric arterial rings in vitro were examined. 3. Endothelium-independent arterial relaxations to isoprenaline and nitroprusside (SNP) were attenuated in aged rats. Increased dietary Q10 clearly enhanced the relaxation to isoprenaline, but did not affect the response to SNP. In addition, vasodilation of noradrenaline-precontracted rings to acetylcholine (ACh), which was also impaired in aged vessels, was improved after Q10 supplementation. Cyclooxygenase inhibition with diclofenac enhanced the relaxation to ACh only in young rats, while it abolished the difference between the old controls and Q10 supplemented rats, suggesting that the improved endothelium-dependent vasodilation observed in Q10 supplemented rats was largely mediated by prostacyclin (PGI2). 4. In conclusion, long-term Q10 supplementation improved endothelium-dependent vasodilation and enhanced beta-adrenoceptor-mediated arterial relaxation in senescent Wistar rats. The mechanisms underlying the improvement of endothelial function may have included augmented endothelial production of PGI2, increased sensitivity of smooth muscle to PGI2, or both.
