Factors influencing the vascular action of dopamine in the canine mesenteric bed.
The effect of dopamine on the mesenteric arterial bed was investigated in dogs anaesthetized with pentobarbital sodium. The vascular responses to dopamine in a branch of the superior mesenteric artery supplying a segment of the small intestine were measured with a flowmeter probe and visualized by infrared telethermography or, in a separate series of dogs, were obtained by the direct determination of arterial resistance--changes during perfusion with constant flow. It was found that the mesenteric action of dopamine (given i.v. in the submaximal dose of 16 micrograms.kg-1.min-1 or intraarterially up to a dose of 40 micrograms.min-1) is primarily mediated via dopaminergic vasodilator and a alpha-adrenergic vasoconstrictor receptors, the net result of this competition usually being moderate vasodilation under natural conditions. The contribution of beta-adrenergic vasodilation to the mesenteric dopamine action is minimal as evidenced by beta-blockade with oxprenolol. By blocking the alpha-component with phentolamine (1.0 mg.kg-1) an almost threefold increase of the vasodilation was obtained in resistance. Because of the concomitant reversal of the systemic hypertensive dopamine action to hypotension, the net flow increase remained essentially unchanged. It was concluded that unless the degree of alpha-stimulation is restrained and proper control of blood pressure is ensured, it is not possible to recommend that dopamine be used in the therapy of mesenteric vascular disorders.
Dóbi
I
I
Clinic of Cardiovascular Surgery, Semmelweis University Medical School, Budapest, Hungary.
Kékesi
V
V
D000818:Animals; D001783:Blood Flow Velocity; D004285:Dogs; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D011954:Receptors, Dopamine / Q000502:physiology; D013152:Splanchnic Circulation / Q000187:drug effects*; D013817:Thermography; D014664:Vasodilation / Q000187:drug effects
D011942:Receptors, Adrenergic, alpha; D011954:Receptors, Dopamine; D004298:Dopamine