AJP - Heart and Circulatory Physiology, Vol 258, Issue 6 1660-H1667, Copyright © 1990 by American Physiological Society
Enhanced alpha-adrenergic vasoconstriction by n-3 fatty acids in conscious dogs
D. Kenny, H. L. Brooks and D. C. Warltier
Department of Medicine (Division of Cardiology), Medical College of Wisconsin, Milwaukee 53226.
The effect of dietary fish oil supplementation on cardiac function and the
pressor response to selective agonists of postjunctional alpha 1- and alpha
2-adrenoceptors was investigated in chronically instrumented dogs (n = 12).
Following ganglionic, cholinergic, and beta-adrenergic blockade, dose
responses to phenylephrine (0.3-1.2 micrograms/kg iv), a selective alpha
1-adrenoceptor agonist, and azepexole (B-HT 933, 5-20 micrograms/kg iv), a
selective alpha 2-adrenoreceptor agonist, were obtained in conscious dogs.
Fish oil capsules containing eicosapentaenoic acid (1.12 g) and
docosahexaenoic acid (480 mg) were administered orally twice daily for 1
wk, and dose-response curves were repeated. Dose-response curves were again
obtained 1 wk after fish oil was discontinued. Fish oil supplementation
resulted in significantly (P less than 0.05) increased arterial pressure at
rest, and after autonomic nervous system blockade there was an increase in
peripheral vascular resistance. Cardiac output was reduced in fish
oil-treated dogs during autonomic nervous system blockade. The pressor
response to selective alpha 1- and alpha 2-adrenoceptor stimulation was
increased secondary to elevated peripheral vascular resistance.
Hemodynamics and exaggerated vascular reactivity returned to control 1 wk
after dietary fish oil was discontinued. The results of this study
demonstrate that dietary fish oil supplementation produces an increase in
arterial pressure via peripheral vasoconstriction and that the vascular
response to alpha-adrenergic stimulation is exaggerated.
