Vasomotor responses of newly developed coronary collateral
vessels.
Kinn, James W., John D. Altman, Mark W. Chang, Robert J. Bache.
Division of Cardiology, Department of Medicine, University of
Minnesota Medical School, Minneapolis, Minnesota, USA
APStracts 2:0563H, 1995.
Well developed coronary collateral vessels contain an abundant
muscular media and can undergo active vasomotion. However, early
after coronary occlusion, coronary collateral vessels are thin walled
with little smooth muscle, suggesting that vasomotor capability might
be limited. Consequently, this study determined whether newly
developed coronary collateral vessels have active vasomotor activity,
and whether endothelial function in these newly developed vessels is
impaired. Retrograde blood flow was measured as an index of coronary
collateral blood flow approximately two weeks after embolic occlusion
of the anterior descending coronary artery of dogs. Agonists were
administered into the left main coronary artery to reach collaterals
originating from the left coronary system. Baseline retrograde blood
flow was 25.1 +/- 2.7 ml/min and increased to 36.7 +/- 3.5 ml/min
after nitroglycerin, 6 [mu]g/kg/min (p<0.05). Cyclooxygenase
blockade with indomethacin, 5 mg/kg i.v., decreased retrograde
collateral blood flow to 16.8 +/- 2.6 ml/min (p <0.05).
Subsequent administration of acetylcholine increased retrograde flow
to 29.4 +/- 3.7 ml/min (p < 0.05), indicating intact endothelium
mediated vasodilation. Inhibition of nitric oxide synthase with N
-nitro-L-arginine (LNNA) further decreased coronary collateral
retrograde flow to 12.0 +/- 2.8 ml/min (p < 0.05) and markedly
blunted the response to acetylcholine. These findings demonstrate
substantial vasomotor capability even early during coronary
collateral development, and indicate that both nitric oxide and
cyclooxygenase dependent endothelial mechanisms are intact.
Received 5 July 1995; accepted in final form 6 December 1995.
APS Manuscript Number H618-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95