Effect of angiotensin II and norepinephrine on release of prostaglandins E2 and I2 by the perfused rat mesenteric artery

Prostaglandin E₂ (PGE₂) and 6 keto-PGF_1α, the stable metabolite of prostacyclin (PGI₂), have been measured in the effluent of perfused rat mesenteric arteries by the use of a sensitive and specific radioimmunoadday (RIA) method. The PGE₂ and 6-keto-PGF_1α were continuousyl released by the unstimulated mesenteric artery over a period of 145 min. After 100 min of perfusion the release of PGE₂ and 6-keto-PGF_1α was 4.5 ± 8.4 pg/min and 254 ± 75 pg.min respectively, which is in accord with the general belief that PGI₂ is the major PG synthesized by arterial tissue. Angiotensin II (AII) 5 ng/ml) induced an increased of PGE₂ and 6-keto-PGF_1α release without changing the perfusion pressure. The effect of norepinephrine (NE) injections on release of PGs depended on the duration of the stabilization period. The changes of perfusion pressure induced by NE were not related to changes in release of PGs. Thus, it seems that the increase of PG release induced by AII and NE was due to a direct effect of the drugs on the vascular wall. This may represent an important modulating mechanism in the regulation of vascular tone.