Exercise training improves endothelium-mediated vasorelaxation after chronic coronary occlusion

The present study evaluated combined effects of chronic coronary occlusion and exercise training on endothelial function. Gradual occlusion was produc ed by placement of an ameroid constrictor around the proximal left circumfl ex (LCX) coronary artery of female swine. Two months after placement of the ameroid, animals were restricted to their pens or exercise trained for 16 wk. Epicardial arteries (>500 mu m ID) were isolated from the collateral-de pendent LCX coronary artery distal to the occlusion and the nonoccluded lef t anterior descending (LAD) coronary artery. Bradykinin- and ADP-mediated r elaxation of LCX and LAD coronary arteries was enhanced after exercise trai ning. Inhibition of nitric oxide synthase with N-G-nitro-L-arginine methyl ester decreased bradykinin- and ADP-mediated relaxation in LCX and LAD myoc ardial regions. Importantly, combined inhibition of effects of endothelium- derived hyperpolarizing factor with increased extracellular K+ (20-30 mM) a nd nitric oxide synthase completely abolished coronary LAD and LCX relaxati on to bradykinin. Our data indicate that exercise training improves endothe lium-mediated relaxation of arteries isolated after chronic coronary artery occlusion, Likely as a result of enhanced production of nitric oxide and e ndothelium-derived hyperpolarizing factor.