Prostaglandins and local circulatory control.

The present paper reviews several lines of investigation have provided highly suggestive evidence for an important regulatory role for prostaglandins in the microcirculation. Aside from their profound vasodepressor effects in a number of animal species, including man, and their vasodilator activity in many local circulatory beds, endogenously administered prostaglandins of the E and A type also appear to reduce vascular responsiveness to a variety of vasoconstrictor agents. Furthermore, inhibition of endogenous synthesis and release of prostaglandins leads to a potentiation of vasoconstrictor responses. Thus it appears that the release of prostaglandins, an event that accompanies or is a consequence of vasoconstriction, can moderate the constrictor response and in this manner can contribute to the control of vascular reactivity. Administration of inhibitors of prostaglandin synthesis to tissues that under basal experimental conditions release prostaglandins, causes not only a decrease in prostaglandin output but also an increase in resting perfusion pressure. These results support the concept that prostaglandins that are released are essential in the control of vascular tone and resistance. Other evidence also suggests that prostaglandins participate in a variety of vascular responses, including the mediation of bradykinin vasodilation, functional hyperemia, and reactive hyperemia.