ENDOTHELIUM-DEPENDENT VASODILATION OF PROXIMAL CORONARY-ARTERIES FROMEXERCISE-TRAINED PIGS

We recently reported that alpha-adrenergic vasoconstriction is blunted and adenosine-induced vasodilation is enhanced in proximal coronary a rteries of exercise-trained miniature swine [C. L. Oltman, J. L. Parke r, H. R. Adams, and M. H. Laughlin. Am. J. Physiol. 263 (Heart Circ. P hysiol. 32): H372-H382, 1992]. The purpose of the present study was to determine whether this model of exercise training also alters endothe lium-dependent vasodilator responses of proximal coronary arteries. Fe male Yucatan miniature swine were exercise trained (ET) on a motor-dri ven treadmill or were cage confined (Sed) for 13-20 wk. Exercise toler ance, heart weight-to-body weight ratios, and skeletal muscle oxidativ e capacity were all significantly greater in ET than in Sed animals. V asodilator responses were evaluated in vitro by determining concentrat ion-response curves by using vascular rings (3.5-4 mm in axial length) isolated from right and left coronary arteries. Vasorelaxation respon ses were determined, after tone had been produced with either 30 mu M prostaglandin F-2 alpha, 30 mM KCl, or 30 nM endothelin. Concentration -response curves were obtained to endothelium-dependent vasodilators i ncluding bradykinin (10(-9)-10(-6) M), substance P (10(-12)-10(-6) M), clonidine (10(-9)-10(-6) M), serotonin (10(-10)-10(-5) M), and the Ca 2+ ionophore A-23187 (10(-10)-10(-6) M). Endothelium-independent vasod ilator responses to sodium nitroprusside (10(-9)-10(-4) M) were not di fferent between arteries from Sed and ET. Bradykinin, substance P, and A-23187 were potent vasodilators in arteries from both groups, wherea s serotonin and clonidine did not consistently produce vasodilation. T here were no significant differences between the vasodilator responses of arteries from ET and Sed pigs for any agent used in this study. We conclude that endothelium-dependent vasodilation of proximal coronary arteries is not altered in exercise-trained miniature swine.