Arginine-Vasopressin modulates intracelullar pH via V1 and V2 receptors in renal collecting Duct cells

C. CAPURRO; V. RIVAROLA; P. FORD

Buenos Aires, Argentina

Conferencia; XXII Latin-American and I Ibero-American Congress of Physiolical Sciences.; 2006

SAFisiol y ALACF

Arginine vasopressin (AVP) has been proposed to be involved in the modulation of acid-base transporters; however, the nature of the mechanism underlying AVP action on intracellular pH (pHi) in the cortical collecting duct (CCD) is not yet defined clearly. The aim of the present study was to elucidate the proteins implicated in AVP modulation of pHi, as well as the receptors involved in these responses in a rat cortical collecting duct cell line (RCCD1) that has previously been shown to be a good model of CCD cells. Intracellular pH (pHi) was spectrofluorometrically studied, by the fluorescent dye BCECF, in cell monolayers grown on permeable filters, either in basal conditions or after stimulation by basolateral 10-8 M AVP. Specific V1- or V2-receptor antagonists were also used. Our results showed that AVP, via V2-receptor, induced a biphasic response: a rapid alkalinization followed by an acidification. The initial alkalinization was completely abolished by low doses of HOE-694, a highly specific inhibitor of the Na+/H+ exchanger, demonstrating an activation of basolateral NHE-1 isoform of this transporter. The secondary acidification was completely blocked by glibenclamide indicating the participation of CFTR. Both responses were dependent on extracellular Ca2+. On the other hand, AVP stimulation of V1-receptor resulted in an acidification due to an increase in Cl-/HCO3- exchange activity dependent on intra and extracellular Ca2+. We conclude that in CCD cells AVP selectively activates, via a complex of V1 and V2 receptor-mediated actions, three proteins involved in ions transport and/or in pHi regulation.