Functional and molecular adaptation of Cl-/HCO3-. exchanger to acute and chronic alkaline media in renal cells

RIVAROLA, VALERIA; FORD, PAULA; CHARA, OSVALDO; PARISI, MARIO; CAPURRO, CLAUDIA

CELLULAR PHYSIOLOGY AND BIOCHEMISTRY : INTERNATIONAL JOURNAL OF EXPERIMENTAL CELLULAR PHYSIOLOGY, BIOCHEMISTRY, AND PHARMACOLOGY.

Karger

Lugar: Basilea; Año: 2005 vol. 16 p. 271 - 280

1015-8987

The Cl-/HCO3- exchanger (AE) is one of the mechanisms that cells have developed to adjust pH Despite its importance, the role of AE isoforms in controlling steady-state pH during alkalosis has not been widely investigated. In the present study, we have evaluated whether conditions simulating acute and chronic metabolic alkalosis affected the transport activity and protein levels of Cl-/HCO3-  exchangers in a rat cortical collecting duct cell line (RCCD1). pHi was monitored using the fluorescent dye BCECF in monolayers grown on permeable supports. Anion exchanger function was assessed by the response of pHi to acute chloride removal. RT-PCR and immunoblot assays were also performed. Our results showed that RCCD1 cells express two members of the anion exchanger gene family: AE2 and AE4. Functional studies demonstrated that while in acute alkalosis pHi became alkaline and was not regulated, after 48 h adaptation; steady-state pHi reached a value similar to the physiological one. Chronic treated cells also resulted in a 3-fold rise in Cl-/HCO3-  exchange activity together with a 2.2-fold increase in AE2, but not AE4, protein abundance. We conclude that RCCD1 cells can adapt to chronic extracellular alkalosis reestablishing its steady-state pHi and that AE2 would play a key role in cell homeostasis.