Responses to dopamine of isolated human gastroepiploic arteries.

Responses to dopamine were compared in helical strips of human gastroepiploic arteries (proximal portion) and their epiploic branches (distal portion), partially contracted with prostaglandin F2 alpha. Dopamine produced a dose-related contraction in the proximal arteries, which was reversed to a relaxation by treatment with phentolamine. On the other hand, the distal arteries responded to low concentrations of dopamine with relaxations and to high concentrations with contractions. The relaxant response was selectively suppressed by treatment with droperidol and reversed to a contraction by SCH23390, but was not influenced by domperidone and propranolol. The amine-induced relaxation was not reduced by removal of the endothelium. The distal arteries, in which dopamine elicited a relaxation, responded to norepinephrine with dose-related contractions, which were suppressed by phentolamine but were not reversed to relaxations. It may be concluded that dopamine contracts human gastroepiploic arteries of the proximal portion, due to a predominant activation of alpha-adrenoceptors, and dilates the distal arteries by acting preferentially on dopaminergic DA1-receptors, possibly residing in smooth muscle. In the distal arteries, the ability of norepinephrine to activate alpha-adrenoceptors appears to be evidently higher than that of dopamine.