ROLE OF NA/H EXCHANGER IN CELL VOLUME REGULATION IN A RAT CORTICAL COLLECTING DUCT CELL LINE

FORD PAULA; KIERBEL ARLINET; RIVAROLA VALERIA; CHARA OSVALDO; BLOT-CHABAUD MARCEL; FARMAN NICOLETTE; PARISI MARIO; CAPURRO CLAUDIA

Buenos Aires, Argentina

Congreso; XIV International Biophysics Congress; 2002

IUPAB - SAB

ROLE OF NA/H EXCHANGER IN CELL VOL­UME REGULATION IN A RAT CORTICAL COLLECTING DUCT CELL LINE Paula Ford1, Arlinet Kierbel1, Valeria Rivarola1, Osvaldo Chara1, Marcel Blot-Chabaud2, Nicolette Farman2, Mario Parisi´, Claudia Capurro1; ´Universidad de Buenos aires - Facultad de Medicina, Argentina, 22 Unidad 478 INSERM, Faculte de Medecine Xavier Bichat, France The Na/H isoforms (NHE) display different tubular and membrane localization and are involved in different functions. This study examines the transporters involved in pHi regulation and its rela­tion with cell volume regulation in a rat cortical collecting duct cell line (RCCD1). pHi was spectrofluorometry studied by using the pH-sensitive fluorescent BCECF/AM. Monolayers, grown on permeable filters, were placed on special holders allowing inde­pendent access to apical and basolateral compartments. Acid load was induced by a NHUC1 prepulse. pHi recovery after an acid load was basolateral, but not apical, Na-dependent and mainly sensitive to EffA. Exposure of RCCD1 cells to basolateral hyperosmolality (mannitol or sucrose) induced an amiloride-sensitive-alkalinization. This response was not observed when hyperosmo­lality was induced by urea, indicating that tonicity activates Na/H exchange. Arginine-vasopressin (AVP) also induced an amiloride-sensitive alkalinization. RT-PCR and Western-blot studies demon­strated the presence of NHE-1 and NHE-2 isoforms but not NHE-3 and NHE-4 in RCCD1 cells. We concluded that basolateral NHEs play an important role in pHi regulation after an acid load and in these cells NHEs are also activated by hypertonicity and AVP, both processes probably involved in RVI response.