Exercise Training Restores Coronary Arteriolar Dilation to NOS Activation Distal to Coronary Artery Occlusion

Abstract

Objective— Exercise training has been shown to restore vasodilation to nitric oxide synthase (NOS) activation in arterioles distal to coronary artery occlusion. Because reactive oxygen species are generated during NOS uncoupling and the production of vasodilator H 2 O 2 is increased during exercise in patients with coronary disease, we proposed that H 2 O 2 may contribute to the restoration of vasodilation in porcine coronary occlusion model. Methods and Results— Left circumflex (LCX) coronary artery of miniature swine was progressively occluded for 8 weeks followed by exercise training (EX; 5 days/wk treadmill) or sedentary (SED) protocols for 12 weeks. Arterioles were isolated from distal LCX and nonoccluded left anterior descending (LAD) artery for in vitro study. Vasodilation to NOS activators adenosine and ionomycin was impaired in SED LCX, but not LAD, arterioles. This impairment was restored by L-arginine. NO production induced by adenosine was also reduced in SED LCX arterioles. EX had no effect on LAD arterioles but improved NO production and restored dilation of LCX arterioles. NOS blockade (L-NAME) inhibited vasodilation to NOS activators in LAD (SED & EX) arterioles but was ineffective in SED LCX arterioles. In EX LCX arterioles, vasodilation to NOS activators was slightly inhibited by L-NAME but abolished by catalase. H 2 O 2 production was markedly increased by adenosine in EX LCX arterioles. Conclusions— This study demonstrates that endothelium-dependent NO-mediated dilation is impaired in SED LCX arterioles and that EX training restores the impaired function. It appears that H 2 O 2 , in addition to NO, contributes significantly to EX-induced restoration of endothelium-dependent dilation of coronary arterioles distal to occlusion.