Possible contributions of endogenous prostaglandins to the control of blood pressure.

Prostaglandins are primarily local or tissue hormones which have their effects at or near the site of release and are metabolized before reaching the arterial circulation. A possible exception is prostaglandin A-2, which has been proposed as a circulating hormone; however, there is no evidence that prostaglandin A-2 is biosynthesized in the mammalian kidney or even in extrarenal tissues. The prostaglandin generated and released in the kidney is predominantly E-2. Some blood vessels also synthesize prostaglandins intramurally, where their local release influences vascular tone and reactivity. Endogenous prostaglandin E-2 production contributes to the regulation of blood pressure by (1) opposing the vasoconstrictor and antidiuretic actions of circulating pressor hormones; (2) braking the release of norepinephrine from vasoconstrictor nerves; and (3) participating in the control extracellular fluid volume through its renal hemodynamic actions.