Pathological role of aquaporin-2 in impaired water excretion and hyponatremia.

Abstract

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.

• Authors: S Ishikawa, T Saito, K Kasono
• Journal: Journal of neuroendocrinology (J Neuroendocrinol) Vol. 16 Issue 4 Pg. 293-6 (Apr 2004) ISSN: 0953-8194 [Print] United States
• PMID: 15089964 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Review)

Chemical References

• Aqp2 protein, rat
• Aquaporin 2
• Aquaporins
• Water

Topics

• Animals
• Aquaporin 2
• Aquaporins (genetics, metabolism)
• Hyponatremia (metabolism)
• Inappropriate ADH Syndrome (metabolism)
• Kidney Tubules, Collecting (metabolism)
• Rats
• Water (metabolism)
• Water-Electrolyte Balance (physiology)