Osmoreceptors in the hypothalamus stimulates the posterior pituitary gland to release vasopressin (ADH) into the bloodstream when blood osmolarity is high and blood pressure is low due to a low water volume in the blood.
Via the bloodstream vasopressin is transferred to its target receptor located in the basolateral membrane of the epithelia in the renal collecting duct. The vasopressin binds to V2 receptors. This stimulates the insertion of Aquaporin 2 (AQP2) water channels into the apical membrane of epithelia resulting in water now being absorbed into the blood stream. The blood pressure increases as the water volume in the blood rises. This mechanism is used by the body to prevent hypotension.
Related subjects: Renin-Angiotensin System,