Abstract
Disorders of water balance are a disease commonly encountered in our clinical practice. Analysis of vasopressin receptor type II (V2R) is essential to understand the physiology of water balance and it is used as a biological prototype of G protein-coupled receptors (GPCRs). Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a syndrome of inappropriate antidiuretic hormone secretion (SIADH) with low plasmatic vasopressin. The evidence on the role of V2 receptor and of aquaporin (AQP) in the mechanism of action for antidiuretic hormone (ADH) was based on the identification of protein gene mutations in patients with nephrogenic diabetes insipidus and NSIAD syndrome. V2R activating mutations were found in patients with NSIAD, contrasting with the numerous V2R inactivating mutations related to X-linked mutations described in patients with nephrogenic diabetes insipidus.