The action of peptides on the adrenal medulla. Release of adrenaline by bradykinin and angiotensin

The present experiments show that bradykinin and angiotensin are potent releasers of the medullary hormones, probably mainly adrenaline, from the suprarenal glands. Angiotensin is more potent in this respect than any other known substance. These findings were the outcome of a chance observation made when assaying bradykinin by its depressor action on the arterial blood pressure of the cat. On trying to render the assay more sensitive by removing the abdominal viscera and injecting the bradykinin through the central stump of the coeliac artery at its origin from the abdominal aorta above the suprarenals, bradykinin caused a fall, followed after 20-30 sec by a pronounced rise, in arterial blood pressure associated with acceleration of heart rate. The pressor effect and the cardio-acceleration were abolished after removal of the suprarenal glands and were therefore due to release of their medullary hormones. Such an action of bradykinin has been described in rabbits and rats (Lecomte, Troquet & Dresse, 1961), but no quantitative data of the release have been reported. We therefore investigated quantitatively this adrenaline-releasing effect of bradykinin and related kinins. On extending the experiments to angiotensin an extreme sensitivity of the suprarenal medulla to this peptide was revealed. Three other peptides, vasopressin, oxytocin and substance P, did not have this property. Examined under similar conditions they did not cause a detectable release of adrenaline from the suprarenals.