Differential Role of Na+/H+ Exchange Isoforms NHE-1 and NHE-2 in a Rat Cortical Collecting Duct Cell Line

Abstract

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.

Increased Na+/H+ exchanger activity on the apical surface of a cilium-deficient cortical collecting duct principal cell model of polycystic kidney disease

“…Similar results were obtained from two other CCD PC monolayer clones from the mutant mice. These data are in agreement with previous observations (8,12,40,41) that CCD PCs with well-formed apical monocilia exhibit mainly, if not exclusively, basolateral NHE activity.…”

“…In the current study, we present immunohistochemical evidence consistent with apical NHE expression of cilium-deficient principal cells derived from the renal collecting duct. In most studies (8,12,40,41), except for a couple (15,17), investigators find NHE expression exclusively on the basolateral surface of collecting duct cells. Indeed, we also found NHE1 predominantly localized to the basolateral membrane of collecting duct cells in kidney sections from control vs. orpk mice (Fig.…”

Effect of NHE1 antisense gene transfection on the biological behavior of SGC-7901 human gastric carcinoma cells

“…These form the gene family of membrane exchange protein [7][8][9][10] . The different subtypes have different number and distribution, different pharmacological properties, and are regulated by different factors.…”

Functional and Molecular Adaptation of Cl^-/HCO₃^- Exchanger to Chronic Alkaline Media in RenalCells

“…RCCD 1 monolayers, grown on permeable filters, were inserted between two lucite frames, separating two fluid compartments when diagonally placed in a quartz cuvette as previously reported [11]. Free access both to the apical and basolateral baths was possible.…”

“…The aim of the present work was to study whether conditions simulating acute or chronic metabolic alkalosis affected the transport activity and protein levels of Cl -/HCO 3 -exchanger. For this purpose we have used a rat cortical collecting duct cell line (RCCD 1 ), which exhibits features of both principal and intercalated cells, previously shown to be a good model of collecting duct cell function [7][8][9][10][11]. pH i was monitored using the fluorescent dye 2',7'bis(2-carboxyethyl)-5-(and-6) carboxyfluorescein (BCECF) in monolayers grown on permeable supports, allowing independent and free access to the apical or the basolateral compartments.…”