Mechanism of arachidonic acid induced vasodilatation in the intact rat intestine

ABSTRACT

The dose dependency and mechanism of arachidonic acid [AA]-induced change of total superior mesenteric blood flow [MBF] was investigated in anaesthetized albino rats. MBF of the intact autoperfused mesentery was measured with an extracorporeal electromagnetic flow probe. Direct measurements of systemic blood pressure [BP] were also determined. Intramesenteric arterial [IMA] bolus injections of 10-40 ug of AA caused dose-dependent vasodilatation and decrease in mesenteric vascular resistance [MVR]. Mesenteric vascular responses to AA were abolished by indomethacin 5 mg/kg I.V. The preparation was capable of active dilatation when challenged with acetyl choline [ACh] and of active constriction when angiotensin II [A II] was injected. Prostaglandin I2, [PGI 2], PGE 2 and PGD 2 caused mesenteric vasodilatation, whereas PGF 2gamma caused mesenteric vasoconstriction. These results indicate that cyclooxygenase derived product [S] are responsible for the mesenteric vasodilator effect of AA in the intact rat mesenteric preparation