Prostacyclin Release and the Modulation of Some Vasoactive Hormones

Prostaglandin release into the circulation of the dog was studied by means of the blood-bathed bioassay system of Vane. Bradykinin, angiotensin II and angiotensin I selectively released a prostacyclin-like substance into the circulation, whereas no release was detected with adrenaline, noradrenaline, 5-hydroxytryptamine or acetylcholine. Release induced by bradykinin was mainly of renal origin, whereas that induced by the angiotensins was of more widespread origin, including the lungs and kidneys. No thromboxane A2 or prostaglandin-like substance could be detected from blood by any of these stimuli. Prostacyclin released by bradykinin contributed to the vascular actions of the kinin as indicated by treatment with cyclo-oxygenase inhibitors. Prostacyclin release also contributed to a reduced pressor effect of angiotensin II. This study indicates that prostacyclin release induced by the vasoactive peptides modulates some of their vascular actions.