Oxytocin: One of the Factors for Regulating AQP2 Localization and Urinary AQP2 Excretion

Aquaporin-2 (AQP2), an essential water channel for urinary concentration, is mainly located in the apical plasma membrane of collecting duct epithelial cells, and vasopressin is the major factor for regulation of AQP2 expression in the kidney(Nielsen et al., 1993,Nielsen et al., 1995, (Ishibashi et al., 1997). However, there has been some evidences of a moderate amount of basolateral localization of AQP2 at least in the inner medullary collecting duct (IMCD) (Nielsen et al., 1993), and vasopressin-independent mechanisms of AQP2 regulation should exist(Marples et al., 1995a,Ecelbarger et al., 1997, Ecelbarger et al., 1998,Marples et al., 1998).