Is Angiotensin II a potent vasodilator or vasoconstrictor?

Angiotensin II is recognized primarily as a potent vasoconstrictor. Its role in the renin-angiotensin-aldosterone system (RAAS) is crucial for regulating blood pressure and fluid balance in the body. When blood pressure drops, the kidneys release renin, which ultimately leads to the production of angiotensin II from angiotensin I through the action of angiotensin-converting enzyme (ACE).

The vasoconstrictor effect of angiotensin II occurs through its binding to specific receptors, leading to the contraction of smooth muscle in the walls of blood vessels. This contraction results in an increase in peripheral vascular resistance, which raises blood pressure. Additionally, angiotensin II also stimulates the release of aldosterone from the adrenal glands, promoting sodium and water reabsorption by the kidneys, which further contributes to increased blood volume and blood pressure.

While angiotensin II does have complex roles in the body, its primary and most notable effect is vasoconstriction, making it an important target in the treatment of hypertension and heart failure.