Cl⁻ channels in intact human T lymphocytes

Summary

We recently described a large, multiple-conductance Cl⁻ channel in excised patches from normal T lymphocytes. The properties of this channel in excised patches are similar to maxiCl⁻ channels found in a number of cell types. The voltage dependence in excised patches permitted opening only at nonphysiological voltages, and channel activity was rarely seen in cell-attached patches. In the present study, we show that Cl⁻ channels can be activated in intact cells at physiological temperatures and voltages and that channel properties change after patch excision.

Maxi-Cl⁻ channels were reversibly activated in 69% of cellattached patches when the temperature was above 32°C, whereas fewer than 2% of patches showed activity at room temperature. Upon excision, the same patches displayed large, multiple-conductance Cl⁻ channels with characteristics like those we previously reported for excised patches. After patch excision, warm temperatures were not essential to allow channel activity; 37% (114/308) of inside-out patches had active channels at room temperature. The voltage dependence of the channels was markedly different in cell-attached recordings compared with excised patches. In cell-attached patches, Cl⁻ channels could be open at cell resting potentials in the normal range. Channel activation was not related to changes in intracellular Ca²⁺ since neither ionomycin nor mitogens activated the channels in cell-attached patches, Ca²⁺ did not rise in response to warming and the Cl⁻ channel was independent of Ca²⁺ in inside-out patches. Singlechannel currents were blocked by internal or external Zn²⁺ (100–200 μm), 4-acetamido-4′ isothiocyanostilbene-2,2′-disulfonate (SITS, 100–500 μm) and 4,4′-diisothiocyanostilbene 2,2′disulfonate (DIDS, 100 μm). NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate) reversibly blocked the channels in inside-out patches.