What physiological effect does ADH (vasopressin) have on blood vessels?

ADH, or antidiuretic hormone (also known as vasopressin), primarily functions to regulate water balance in the body, but it also has notable effects on blood vessels. When ADH is released, it causes the smooth muscle in blood vessels to constrict, which increases the vascular resistance. This constriction leads to an increase in blood pressure, making the correct response reflect the role of vasopressin in maintaining hemodynamic stability, particularly during states of low blood volume or blood pressure, such as in dehydration or hemorrhage.

In addition to its primary role in the kidneys, where it promotes water reabsorption to concentrate urine, the action on blood vessels is crucial for processes like regulating systemic blood pressure and compensating for blood loss. Thus, the physiological effect of ADH on blood vessels is well characterized by its ability to increase blood pressure through vasoconstriction.