The major action of angiotensin II is which of the following?

• A. increase pituitary secretion of vasopressin
• B. increase vasoconstriction
• C. increase parathormone secretion by the parathyroid
• D. decrease adrenal secretion of aldosterone

Answer: (B)

Angiotensin II primarily constricts blood vessels, rapidly increasing systemic vascular resistance and arterial pressure. This vasoconstrictive action, mediated by AT1 receptors on vascular smooth muscle, is the main way it helps maintain blood pressure during volume loss or reduced renal perfusion.

In addition to this direct effect, angiotensin II stimulates aldosterone release from the adrenal cortex, promoting sodium and water retention to support long-term blood pressure maintenance, and it can promote vasopressin (ADH) secretion. However, these are secondary or supportive actions that work after the immediate vasoconstriction.

Parathyroid hormone secretion is not driven by angiotensin II, and angiotensin II actually increases aldosterone rather than decreasing it.