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Pathological Role of Aquaporin‐2 in Impaired Water Excretion and Hyponatremia
Author(s) -
Ishikawa S.,
Saito T.,
Kasono K.
Publication year - 2004
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.0953-8194.2004.01177.x
Subject(s) - vasopressin , endocrinology , medicine , aquaporin 2 , hyponatremia , arginine vasopressin receptor 2 , antidiuretic , vasopressin receptor , syndrome of inappropriate antidiuretic hormone secretion , arginine vasopressin receptor 1b , tonicity , receptor , antagonist , water channel , mechanical engineering , engineering , inlet
In the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), inappropriately elevated secretion of vasopressin can result in a reduction of antidiuretic efficacy: a phenomenon known as ‘vasopressin escape’. We compared experimental SIADH with 1‐deamino‐8‐ d ‐arginine vasopressin (dDAVP)‐excess rats, where both groups received continuous subcutaneous administration of dDAVP by osmotic minipump but the SIADH rats also received a liquid diet that induced hyponatraemia. The SIADH rats, but not the dDAVP excess rats, showed a marked attenuation of urinary concentrating ability. Vasopressin V 2 receptor binding capacity and mRNA expression were similar between the two groups, but the SIADH rats showed a diminished up‐regulation of aquaporin‐2 (AQP‐2) mRNA and protein expression. These findings indicate the presence of tonicity‐response regions in the AQP‐2 promoter gene, and that either hypervolemia or hypotonicity may attenuate the postreceptor signalling of vasopressin in renal collecting duct cells in SIADH rats.