Regulation of extracellular fluid volume and blood pressure by pendrin

Abstract

Na + is commonly designed as the culprit of salt-sensitive hypertension but several studies suggest that abnormal Cl - transport is in fact the triggering mechanism. This review focuses on the regulation of blood pressure (BP) by pendrin, an apical Cl - /HCO 3- exchanger which mediates HCO 3- secretion and transcellular Cl - transport in type B intercalated cells (B-ICs) of the distal nephron. Studies in mice showed that it is required not only for acid-base regulation but also for BP regulation as pendrin knock-out mice develop hypotension when submitted to NaCl restriction and are resistant to aldosterone-induced hypertension. Pendrin contributes to these processes by two mechanisms. First, pendrin-mediated Cl - transport is coupled with Na + reabsorption by the Na + -dependent Cl - /HCO 3- exchanger NDCBE to mediate NaCl reabsorption in B-ICs. Second, pendrin activity regulates Na + reabsorption by the adjacent principal cells, possibly by interaction with the ATP-mediated paracrine signalling recently identified between ICs and principal cells. Interestingly, the water channel AQP5 was recently found to be expressed at the apical side of B-ICs, in the absence of a basolateral water channel, and pendrin and AQP5 membrane expressions are both inhibited by K + depletion, suggesting that pendrin and AQP5 could cooperate to regulate cell volume, a potent stimulus of ATP release. © 2011 S. Karger AG, Basel.