Differential role of Na+/H+ exchange isoforms NHE-1 and NHE-2 in a rat cortical collecting duct cell line.
The Na+/H+ exchanger (NHE) constitutes a gene family containing several isoforms that display different membrane localization and are involved in specialized functions. Although basolateral NHE-1 activity was described in the cortical collecting duct (CCD), the localization and function of other NHE isoforms is not yet clear, This study examines the expression, localization, and regulation of NHE isoforms in a rat cortical collecting duct cell line (RCCD1) that has previously been shown to be a good model of CCD cells. Present studies demonstrate the presence of NHE-1 and NHE-2 isoforms, but not NHE-3 and NHE-4, in RCCD1 cells. Cell monolayers, grown on permeable filters, were placed on special holders allowing independent access to apical and basolateral compartments. Intracellular pH (pHi) regulation was spectrofluorometrically studied in basal conditions and after stimulation by NH4Cl acid load or by a hyperosmotic shock. In order to differentiate the roles of NHE-1 and NHE-2, we have used HOE-694, an inhibitor more selective for NHE-1 than for NHE-2. The results obtained strongly suggest that NHE-1 and NHE-2 are expressed in the basolateral membrane but that they have different roles: NHE-1 is responsible for pHi recovery after an acid load and NHE-2 is mainly involved in steady-state pHi and cell volume regulation.
Ford
P
P
Laboratorio de Biomembranas, Depto de Fisiología, Facultad de Medicina, Univ. de Buenos Aires, Paraguay 2155, Piso 7, 1121 Buenos Aires, Argentina.
Rivarola
V
V
Kierbel
A
A
Chara
O
O
Blot-Chabaud
M
M
Farman
N
N
Parisi
M
M
Capurro
C
C
D000818:Animals; D002460:Cell Line; D048429:Cell Size / Q000502:physiology; D005786:Gene Expression Regulation; D006706:Homeostasis / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007685:Kidney Tubules, Collecting / Q000737:chemistry* / Q000502:physiology*; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D020033:Protein Isoforms / Q000737:chemistry / Q000502:physiology; D051381:Rats; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry* / Q000502:physiology*
D020033:Protein Isoforms; C513110:Slc9a2 protein, rat; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1