Microcirculatory effects of prostaglandins.

Abstract

In vivo microscopy was utilized to evaluate the vasomotor action of prostaglandin E1 (PGE1) and prostaglandin F2α (PGF2α) in the mesocecal and cremasteric muscle circulation of the rat. Vessel dimensions were monitored by using a novel system consisting of microscope, image-splitting eyepiece, television camera, videoscreen, and a write-out apparatus giving exact minute to minute measurements of the microvessel lumen diameter. Intravenous administration of PGE1 decreased systemic blood pressure with a concomitant increase in diameter of the metarterioles of the cremaster muscle and a decrease in diameter of the metarterioles of the mesocecum; it effectively inhibited the constrictor effect of topically applied norepinephrine and epinephrine on the mesocecum metarterioles. Constrictor effects of topically applied angiotensin II were not altered. Intravenous PGF2α increased systemic blood pressure with a concomitant decrease in metarteriolar diameter in both the mesocecum and cremaster muscles. The vascular effects of PGE1 could be explained by its apparent ability to block at the postganglionic sympathetic neuroeffector site where PGE1 acts on the vascular tissue, modulating its response to adrenergic stimulants, whereas PGF2α acts as a direct stimulant of the vascular smooth muscle.