Vasopressin acts by:
Water transpo across collecting duct
Water absorption at medullary ducts
Water secretion at loop of Henle
Water transpo at PCT
A i.e. Water transpo across collecting ductVasopressin acts by increasing permeability of collecting ductsQ. to water. The key to the action of vasopressin on collecting duct is aquaporin -2 . The overall effect is retention of water in excess of solute which results in decrease effective osmotic pressure