Water Channels in Health and Disease

Title: Water Channels in Health and Disease
Author: Berl, Tomas
Publisher: Kidney International
Date Published: May 01, 1998
Reference Number: 190
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This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)

In this editorial, Berl discusses the advances made in understanding the hormone, vasopressin, and its role in water-balance disorders, specifically research into the vasopressin-2 receptor (V2R) and the water-transporting protein, aquaporin-2 (AQP2). When vasopressin binds with V2Rs in the kidney collecting duct, it initiates a molecular sequence that results in AQP2s inserting themselves in the apical membrane of the principal cell of the kidney collecting duct. This makes them much more water permeable than usual. This increased water permeability is what allows the kidney collecting duct to reabsorb water, concentrate urine and, therefore, maintain body water balance.

Disorders in either the V2R or AQP2 are the molecular basis of nephrogenic diabetes insipidus (NDI). NDI is a disorder characterized by the kidneys' inability to concentrate urine in response to vasopressin. The primary symptoms of NDI are polyuria (the chronic passage of large volumes of urine) and polydipsia (chronic, excessive thirst).