Effects of exercise training on smooth muscle relaxation and myoplasmic free Ca 2+ (Ca m) responses of coronary arteries distal to chronic occlusion
Academic Article
Overview
Additional Document Info
View All
Overview
abstract
We evaluated combined effects of chronic coronary occlusion and exercise training on vasodilator responsiveness of coronary artery rings (1.0-2.5 mm OD) isolated from sedentary (SED; pen-confined) or exercise-trained (EX; treadmill run, 5 days/wk for 16-20 wk) Yucatan miniature swine. Ameroid occluders were surgically placed on the proximal left circumflex coronary artery (LCX) 8 weeks prior to SED or EX protocols. In SED animals (n=10), relaxation responses to adenosine (ADO;10 -8 to 10 -3 M), but not nitroprusside (NP;10 -10 to 10 -4 M), were significantly (P<0.05) impaired in LCX arteries distal to occlusion, as compared to size-matched unoccluded LAD arteries. In contrast, in EX animals (n=11), neither ADO nor NP-induced relaxation was different in LCX vs LAD arteries. ADO-mediated reductions in simultaneous tension and Ca m measures were impaired in LCX vs LAD arteries isolated from SED, but not EX animals. Preliminary studies (n=5) suggest that relaxation to the -adrenergic agonist, isoproterenol, (ISO; 10 -9 to 10 -6 M) was impaired in LCX vs. LAD arteries, but unlike ADO, ISO-induced relaxation remained impaired in EX animals. Our data suggest exercise corrects impaired ADO-mediated relaxation and Ca m responses associated with chronic coronary occlusion; mechanisms may involve receptor-specific and/or second-messenger (cAMP vs cGMP) pathways.
