Comparison of vascular responses of isolated, perfused simian and canine coronary arteries to adrenergic agonists.

The vascular responses of the isolated, perfused simian left circumflex coronary arteries to adrenergic agonists were compared to those of canine coronary arteries in isolated, perfused preparations. Norepinephrine and epinephrine produced only vasoconstriction in monkey arteries in contrast to vasoconstrictor, vasodilator and biphasic responses of canine coronary arteries. Isoproterenol induced a dose-dependent vasodilatation. Salbutamol, a selective beta 2-agonist, produced either a slight vasodilatation or no response. Phenylephrine, a selective alpha 1-agonist, usually caused a marked vasoconstriction in a dose-related manner in both preparations. Xylazine and clonidine, selective alpha 2-agonists, caused a slight vasoconstriction in low doses, but these two agonists relaxed both preparations in high doses. These observations suggest that adrenoceptor subtypes may be mainly alpha-1 and beta-1 in the large coronary arteries of monkeys and dogs and that the alpha-adrenoceptor is predominant in simian large coronary arteries.