Exercise training enhances vasodilation responses to vascular endothelial growth factor in porcine coronary arterioles exposed to chronic coronary occlusion

Background-Chronic coronary occlusion (CCO) impairs endothelial function of distal collateral-dependent microvasculature; however, long-term exercise training (EX) seems to improve endothelial dysfunction. We hypothesized that EX enhances vasodilation responses to vascular endothelial growth factor (VEGF(165)), mediated via nitric oxide (NO), in arterioles exposed to CCO. Methods and Results-The proximal left circumflex coronary artery (LCx) of female Yucatan miniswine was surgically instrumented with an ameroid occluder to induce CCO; 8 weeks after surgery, animals were randomized into 14-week sedentary (SED) or EX (treadmill; 5 d/wk) protocols. Coronary arterioles (approximate to100 mum in diameter) were isolated from collateral-dependent (LCx) and nonoccluded (left anterior descending; LAD) perfused myocardium of SED and EX animals. Vasodilation was assessed by videomicroscopy and MacLab data acquisition. Responses to VEGF(165) were unaffected by EX in nonoccluded LAD arterioles; in contrast, EX markedly enhanced VEGF(165)-induced vasodilation of collateral-dependent LCx arterioles (P<0.05; EX versus SED). Furthermore, VEGF(165)-induced vasodilation of EX LCx arterioles exceeded that of EX or SED LAD arterioles (P<0.05). Enhanced vasodilation of EX LCx arterioles was abolished by inhibition of NO synthase and tyrosine kinase activity. Combined inhibition of NO synthase and cyclooxygenase decreased VEGF(165)-induced vasodilation of all vessels. Conclusions-EX enhances VEGF(165)-induced vasodilation in arterioles distal to CCO; EX effects seem to be mediated through increases in NO.