The central nervous action of angiotensin on aldosterone secretion and electrolytic balance

By means of the “isolated head” method previously developed and described by one of the authors ( Gr. Benetato), the central nervous action of angiotensin (Ciba hypertensin) on blood pressure as well as its effect on the amount of catecholamine, aldosterone and 17-hydroxycorticosteroids in the lumbosuprarenal blood, were studied in twenty-even chloralosed dogs. The animals were divided into two groups, according to the conditions under which the experiments were carried out: crossed circulation, or perfusion of the isolated head with blood from donor dogs. In 16 experiments, a concomitant study was carried out on changes in blood pressure, hormonal determinations and variations in urinary sodium and potassium in the receivers. Angiotensin administered centrally increases blood pressure in the trunk of the donee by 20–50 mm Hg in both animal groups. The pressor effect persists after central administration of largactyl (10 mgkg body weight). It disappears after atropine (2 mgkg body weight) is administered in the carotid, and is reversed in the animals previously treated with reserpine (2 mgkg body weight intraperitoneally, 12 hr before the experiment). Slow noradrenalin perfusion in the cerobral circulation of the reserpine treated donee re-establishes the pressor effect of angiotensin central administration These data are evidence of the adrenergic nature of the central pressor effect of angiotensin. Increase in lumbosuprarenal blood catecholamines in the donee supports this view. As regards aldosterone secretion and electrolytic balance, it was found that angiotensm administered centrally exercises no effect under the conditions of perfusion of the isolated head. In crossed circulation experiments, however, central administration of angiotensin brings about marked changes in the trunk of the donee affecting both aldosterone secretion and the urine elimination of electrolytes. As aldosterone decreases in the blood of the donee, sodium elimination increases, a fact also illustrated by increase of the Na/K ratio. Since the phenomenon appears only under conditions of crossed circulation and disappears after ablation of the adrenals in the donor animals, it may be assumed that there is an indirect central action of angiotensin on the hydromineral balance through the intermediary of the adrenocortical hormones released from the donor trunk. L'action centrale de l'antiotensine sur la pression sanguine ainsi que son effet sur la teneur en catécholamines, en aldos