AVP and Polydipsia: Arginine vasopressin (AVP) is the antidiuretic hormone that acts on the V2 receptor in the basolateral membrane of the principal cells of the renal collecting duct to promote free water reabsorption via aquaporin-2 channels, expressed on the apical membrane of the principal cells [4,5]. AVP deficiency, previously referred to as central diabetes insipidus, is a condition also marked by polydipsia and polyuria, owing to the absence of the hormone that participates in concentrating urine.