What effect does ADH release have on the blood osmolarity?

ADH (anti diuretic hormone) is a hormone that is released when the hypothalamus detects high blood osmolarity or when blood pressure is low. It is released from the posterior pituitary gland into the blood. ADH binds to vasopressin receptors on the collecting duct which cause enzyme cascades in the epithelial cells of the collecting duct. The enzyme cascade causes vesicles of aquaporins to move towards the plasma membrane and insert onto the apical surfaces of the epithelial cells. Aquaporins are protein channels that facilitate the diffusion of water from the collecting duct lumen back into the epithelial cells and eventually back into the blood. This increases the resorption of water back into the blood which increases the blood volume and decreases the osmolarity.