Characterization of constitutive and acid-induced outwardly rectifying chloride currents in immortalized mouse distal tubular cells #MMPMID28483640
Valinsky WC; Touyz RM; Shrier A
Biochim Biophys Acta Gen Subj 2017[Aug]; 1861 (8): 2007-2019 PMID28483640show ga
Thiazides block Na(+) reabsorption while enhancing Ca(2+) reabsorption in the kidney. As previously demonstrated in immortalized mouse distal convoluted tubule (MDCT) cells, chlorothiazide application induced a robust plasma membrane hyperpolarization, which increased Ca(2+) uptake. This essential thiazide-induced hyperpolarization was prevented by the Cl(-) channel inhibitor 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), implicating NPPB-sensitive Cl(-) channels, however the nature of these Cl(-) channels has been rarely described in the literature. Here we show that MDCT cells express a dominant, outwardly rectifying Cl(-) current at extracellular pH7.4. This constitutive Cl(-) current was more permeable to larger anions (Eisenman sequence I; I(-)>Br(-)>/=Cl(-)) and was substantially inhibited by >100mM [Ca(2+)](o), which distinguished it from ClC-K2/barttin. Moreover, the constitutive Cl(-) current was blocked by NPPB, along with other Cl(-) channel inhibitors (4,4'-diisothiocyanatostilbene-2,2'-disulfonate, DIDS; flufenamic acid, FFA). Subjecting the MDCT cells to an acidic extracellular solution (pH<5.5) induced a substantially larger outwardly rectifying NPPB-sensitive Cl(-) current. This acid-induced Cl(-) current was also anion permeable (I(-)>Br(-)>Cl(-)), but was distinguished from the constitutive Cl(-) current by its rectification characteristics, ion sensitivities, and response to FFA. In addition, we have identified similar outwardly rectifying and acid-sensitive currents in immortalized cells from the inner medullary collecting duct (mIMCD-3 cells). Expression of an acid-induced Cl(-) current would be particularly relevant in the acidic IMCD (pH<5.5). To our knowledge, the properties of these Cl(-) currents are unique and provide the mechanisms to account for the Cl(-) efflux previously speculated to be present in MDCT cells.
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Biochim+Biophys+Acta+Gen+Subj 2017 ; 1861 (8): 2007-2019
