Responsiveness to dopamine of isolated epicardial coronary arteries from humans, monkeys, and dogs.

Dopamine is widely used for the treatment of cardiogenic and hypovolemic shock. This study was undertaken to compare the response to dopamine in epicardial conduit coronary arteries of humans, Japanese monkeys, and dogs, and to determine the mechanism of vasoconstriction and vasodilation. In helical strips of coronary arteries from humans and monkeys partially contracted with prostaglandin F2 alpha, dopamine produced a concentration-related contraction; the human artery contraction was greater. The contractions were reversed to a relaxation by treatment with phentolamine. Relaxation of monkey arteries treated with the alpha adrenoceptor antagonist was not influenced by metoprolol, a beta 1 antagonist, or endothelium denudation, but was reversed to contraction by SCH23390, a dopamine1 receptor antagonist. On the other hand, dog coronary arteries responded to dopamine with a relaxation that was abolished by metoprolol, but not influenced by SCH23390 or butoxamine, a beta 2 antagonist. We conclude that dopamine in clinical doses elicits significant contractions, mediated possibly by alpha adrenoceptors, in human and monkey coronary arteries; thus, care has to be taken when the amine is used in patients with variant angina pectoris. Relaxation of monkey coronary arteries appears to be associated with activation of dopamine1 receptors, whereas those of the dog arteries are mediated mainly by beta 1 receptors.