AJP - Heart and Circulatory Physiology, Vol 256, Issue 4 1148-H1155, Copyright © 1989 by American Physiological Society

ARTICLES

Coronary flow during exercise after selective alpha 1- and alpha 2-adrenergic blockade

X. Z. Dai, E. Sublett, P. Lindstrom, J. S. Schwartz, D. C. Homans and R. J. Bache
Department of Medicine, University of Minnesota Medical School, Minneapolis 55455.

This study was carried out to determine the relative importance of alpha 1- and alpha 2-adrenergic vasoconstriction in opposing the increase in coronary blood flow, which occurs during exercise. The response of left circumflex coronary artery blood flow was examined during treadmill exercise in 16 chronically instrumented dogs during control conditions, after selective alpha 1-adrenergic blockade with intracoronary prazosin, and after alpha 2-blockade with intracoronary idazoxan. During control conditions, graded treadmill exercise resulted in progressive increases of coronary blood flow and decreases of coronary vascular resistance. Prazosin produced highly selective alpha 1-adrenergic blockade; coronary blood flow was significantly higher and coronary vascular resistance significantly lower during all but the heaviest exercise stage after prazosin. Idazoxan produced highly effective, but only moderately selective, alpha 2-adrenergic blockade. However, after idazoxan, coronary blood flow and coronary vascular resistance during exercise were not significantly different from control. Combined alpha 1- and alpha 2-adrenergic blockade was not more effective in increasing coronary blood flow during exercise than was alpha 1-adrenergic blockade alone. These data support a role for alpha 1-adrenergic coronary vasoconstriction in limiting the increase in coronary blood flow, which occurs during exercise, but do not support a role for alpha 2-mediated coronary vasoconstriction during exercise.

This article has been cited by other articles:

				D. J. Duncker and R. J. Bache Regulation of Coronary Blood Flow During Exercise Physiol Rev, July 1, 2008; 88(3): 1009 - 1086. [Abstract] [Full Text] [PDF]

				P. A. Kaufmann, O. E. Rimoldi, T. Gnecchi-Ruscone, T. F. Luscher, and P. G. Camici Systemic nitric oxide synthase inhibition improves coronary flow reserve to adenosine in patients with significant stenoses Am J Physiol Heart Circ Physiol, October 1, 2007; 293(4): H2178 - H2182. [Abstract] [Full Text] [PDF]

				D. Merkus, D. B. Haitsma, O. Sorop, F. Boomsma, V. J. de Beer, J. M. J. Lamers, P. D. Verdouw, and D. J. Duncker Coronary vasoconstrictor influence of angiotensin II is reduced in remodeled myocardium after myocardial infarction Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2082 - H2089. [Abstract] [Full Text] [PDF]

				S. Setty, W. Sun, R. Martinez, H. F. Downey, and J. D. Tune {alpha}-Adrenoceptor-mediated coronary vasoconstriction is augmented during exercise in experimental diabetes mellitus J Appl Physiol, July 1, 2004; 97(1): 431 - 438. [Abstract] [Full Text] [PDF]

				P. Zong, W. Sun, S. Setty, J. D. Tune, and H. F. Downey {alpha}-Adrenergic Vasoconstrictor Tone Limits Right Coronary Blood Flow in Exercising Dogs Experimental Biology and Medicine, April 1, 2004; 229(4): 312 - 322. [Abstract] [Full Text] [PDF]

				D. J. Duncker, R. Stubenitsky, and P. D. Verdouw Autonomic Control of Vasomotion in the Porcine Coronary Circulation During Treadmill Exercise : Evidence for Feed-Forward ß-Adrenergic Control Circ. Res., June 29, 1998; 82(12): 1312 - 1322. [Abstract] [Full Text] [PDF]

				Y. Ishibashi, D. J. Duncker, and R. J. Bache Endogenous Nitric Oxide Masks {alpha}2-Adrenergic Coronary Vasoconstriction During Exercise in the Ischemic Heart Circ. Res., February 1, 1997; 80(2): 196 - 207. [Abstract] [Full Text]

				P. A. Gwirtz Coronary {alpha}1-Constrictor Tone During Renovascular Hypertension Circulation, September 15, 1995; 92(6): 1576 - 1581. [Abstract] [Full Text]