Angiotensin I can stimulate adrenal medulla to secrete adrenaline, which has no obvious effect on direct vasoconstriction; Angiotensin II can make systemic arterioles contract and raise blood pressure; In addition, it can promote adrenal cortex to secrete aldosterone. Aldosterone acts on renal tubules to preserve sodium, water and potassium, which causes blood loss. Increase in volume; increase in Ca ion concentration through Na-Ca channels in cells, causing vasoconstriction, thereby increasing blood pressure (some drugs for hypertension work by antagonizing this effect); Angiotensin III has a weaker vasoconstrictive effect, only 1/5 of Angiotensin II, but the effect of promoting aldosterone secretion is stronger than that of angiotensin II. Element II.