What is one of the actions of angiotensin II?

Angiotensin II plays a significant role in the regulation of blood pressure and fluid balance in the body. One of its key actions is to increase sodium reabsorption in the kidneys. This process occurs primarily in the proximal convoluted tubule and is critical for maintaining blood volume and, consequently, blood pressure.

When angiotensin II is present, it stimulates the reabsorption of sodium ions back into the bloodstream. This reabsorption leads to an increase in osmolarity, prompting the kidneys to also retain water, thereby increasing blood volume. Increased blood volume contributes to elevated blood pressure, which is part of the body's response to low blood pressure or low blood volume situations.

The other choices reflect actions that either do not align with the physiological effects of angiotensin II or describe opposite effects. Angiotensin II generally stimulates sympathetic activity, promotes aldosterone secretion, and causes vasoconstriction, further emphasizing its role in elevating blood pressure. Thus, the increase of sodium reabsorption is one of the hallmark actions of angiotensin II, solidifying its role in maintaining cardiovascular homeostasis.