Inhibition of vasoconstrictor and vasodilator responses by PGE1 in the intestinal vascular bed of the cat

The effects of PGE₁ on vascular resistance, vasoconstrictor responses to sympathetic nerve stimulation and pressor hormones and vasodilator responses to bradykinin and nitroglycerin were investigated in the feline mesenteric vascular bed. Infusions of PGE₁, 1.0 and 0.1 μg/min, into the superior mesenteric artery dilated the mesenteric vascular bed and markedly inhibited vasoconstrictor responses to sympathetic nerve stimulation, norepinephrine and angiotensin and to vasodilator responses to bradykinin and nitroglycerin. The response to the highest dose of bradykinin was reversed to a pressor response during infusion of PGE₁. In contrast, mesenteric perfusion pressure and vasoconstrictor responses to nerve stimulation and pressor hormones and vasodilator responses to bradykinin and nitroglycerin were unchanged during the lowest rate of infusion of PGE₁, 0.01 μg/min. When the decrease in (initial value) vascular resistance was taken into account by expressing vasodilator responses on a percent decrease basis, infusion of PGE₁ reduced or reversed the vasodilator responses to bradykinin whereas the vasodilator responses to nitroglycerin were not altered. Results of these studies suggest that PGE₁ may influence vasomotor tone and responses to pressor hormones and bradykinin in the mesenteric vascular bed of the cat.