Single-Channel Properties of Volume-Sensitive Cl⁻ Channel in ClC-3–Deficient Cardiomyocytes

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It is controversial whether the ClC-3 protein, which is one of the voltage-dependent chloride channel ClC family members, is a candidate for the volume-sensitive outwardly rectifying (VSOR) Cl⁻ channel per se or its regulator. Here, for the first time, we examined the single-channel properties of the VSOR Cl⁻ channel in ventricular myocytes isolated from ClC-3–deficient mice. The single-channel current induced by cell swelling exhibited Cl⁻ selectivity, mild outward rectification, and an intermediate unitary conductance (around 38 pS). A Cl⁻ channel blocker, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), reversibly inhibited the outward current. These single-channel properties were identical with those in ClC-3 expressing wild-type ventricular myocytes. These results indicate that the single-channel activity of the VSOR Cl⁻ channel is independent of the expression of ClC-3 proteins in mouse ventricular myocytes.