AJP - Gastrointestinal and Liver Physiology, Vol 259, Issue 4 605-G610, Copyright © 1990 by American Physiological Society
Hypoxia-induced vasodilation of the feline superior mesenteric artery is not adenosine mediated
L. K. Lockhart and W. W. Lautt
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
The role of adenosine in hypoxia-induced vasodilation was examined in the
intestine of pentobarbital sodium-anesthetized cats. A hollow-fiber fetal
oxygenator was used to selectively reduce the PO2 of the blood supplying
the superior mesenteric artery, thereby inducing hypoxia in the intestines.
Decreasing the PO2 from 109 to 38 Torr caused vascular resistance to
decrease from 10.2 to 7.5 Torr.kg.min.ml-1, a decrease of 2.7
Torr.kg.min.ml-1 or 24%. During selective adenosine receptor blockade with
8-phenyltheophylline, the same decrease in PO2 (from 109 to 40 Torr)
produced a similar decrease in resistance from 5.7 to 3.4 Torr.kg.min.ml-1
or a difference of 2.3 Torr.kg.min.ml-1 (-36%). Thus adenosine is not the
mediator of hypoxia-induced vasodilation in the feline intestine because
blockade of the vasodilating effects of exogenous and presumably endogenous
adenosine did not affect the observed decrease in resistance.
