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.