Objective: Exercise enhances the dilation of the epicardial coronary arteries by vasodilator drugs and blood flow. Our goal was to determine whether coronary artery elastic properties were affected by brief exercise training.
Methods: Arterial pressure and left circumflex coronary artery diameter were measured in dogs. Venous bolus injections of acetylcholine 5μg·kg-1 (ACH) and nitroglycerin 25 μg·kg-1(NTG) or infusions of adenosine 0.5 μM/kg/min (ADO) were given. Fifteen-second coronary artery occlusions were performed. Dogs exercised 2 h·d-1 for 7 d at 10.9 km·h-1. Experiments were repeated. Pressure and coronary radius data were used to calculate vessel wall stress and incremental wall modulus, Einc.
Results: Baseline Einc and radius were not changed by exercise. Before exercise Einc increased similarly from baseline for all vasodilators. After exercise, the increase in Einc with ADO was unchanged. However, the increase was attenuated during ACH, abolished with occlusion, and reversed with NTG despite enhanced dilation.
Conclusion: Data suggest that functional remodeling of epicardial arteries begins soon after starting exercise training, before changes in resting vessel diameter, is mediated by cGMP, and contributes to increased vascular dilation. Brief exercise training enhances the vasodilating capability and elastic properties of large coronary arteries.
Departments of Physiology and Pediatrics, New York Medical College, Valhalla, NY
Submitted for publication January 1997.
Accepted for publication July 1997.
The research was supported in part by Senior NRSA 5F33HL09427-01, and PO-1-43023, HL50142 and HL53053 from the National Heart, Lung and Blood Institute.
Address for Correspondence: Thomas H. Hintze Ph.D., Professor of Physiology, Basic Science Building New York Medical College, Valhalla, NY 10595. E-mail: ThomasHintze@nymc.edu.