Care Flight Entrance Practice Exam

V2 receptor activation in the kidney increases water reabsorption by the collecting ducts. When vasopressin binds to these receptors on principal cells, it triggers a cAMP-PKA signaling cascade that promotes the insertion of aquaporin-2 water channels into the apical membrane. This makes the collecting duct more permeable to water, so more water is reabsorbed from the filtrate back into the bloodstream, concentrating the urine and reducing urine volume.

The other options don’t fit because vasopressin acting on V2 receptors isn’t responsible for widening arterioles, bronchodilating airways, or constricting vessels; those effects involve other receptors (such as V1 for vasoconstriction or different pathways for bronchodilation).