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Cl− channels in intact human T lymphocytes (1992)

Pahapill, P. A. ; Schlichter, L. C.

Springer

The journal of membrane biology 125 (1992), S. 171

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ISSN: 1432-1424

Keywords: chloride channel ; cell-attached patches ; lymphocyte ; T cell ; temperature ; voltage dependence

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: 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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00233356

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Small-conductance chloride channels in human peripheral T lymphocytes (1995)

Schumacher, P. A. ; Sakellaropoulos, G. ; Phipps, D. J. ; [et al.]

Springer

The journal of membrane biology 145 (1995), S. 217-232

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ISSN: 1432-1424

Keywords: Whole-cell recording ; Anion selectivity ; Cl-channel blockers

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract During whole-cell patch-clamp recording from normal (nontransformed) human T lymphocytes a chloride current spontaneously activated in 〉98% of cells (n 〉 200) in the absence of applied osmotic or pressure gradients. However, some volume sensitivity was observed, as negative pressure pulses reduced the current. With iso-osmotic bath and pipette solutions the peak amplitude built up (time constant ≈23 sec at room temperature), a variable-duration plateau phase followed, then the current ran down spontaneously (time constant ≈280 sec). The anion permeability sequence, calculated from reversal potentials was I−, Br− 〉 NO 3 − , Cl− 〉 CH3SO 3 − , HCO 3 − 〉 CH3COO− 〉 F− 〉 aspartate, gluconate, SO 4 2− and there was no measurable monovalent cation permeability. The Cl− current was independent of time during long voltage steps and there was no evidence of voltage-dependent gating; however, the current showed intrinsic outward rectification in symmetrical Cl− solutions. The conductance of the channels underlying the whole-cell current was calculated from fluctuation analysis, using power-spectral density and variance-vs.-mean analysis. Both methods yielded a single channel conductance of about 0.6 pS at −70 mV (close to the normal resting potential of T lymphocytes). The power spectral density function was best fit by the sum of two Lorentzian functions, with corner frequencies of 30 and 295 Hz, corresponding to mean open times of 0.54 and 5.13 msec. The pharmacological profile included rapid block by external application of flufenamic acid (50 μm), 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 100 μm, [6,7-dichloro-2-cyclopentyl-2,3-dihydro-2-methyl-1-oxo-1H-inden-5-y1) oxy] acetic acid (IAA-94, 250 μm) or 100 μm 1,9-dideoxyforskolin. The stilbene derivatives DIDS (4,4′-diisothiocyano-2,2′ di-sulphonic acid stilbene, 500 μm) and SITS (4-acetamido-4′-isothiocyano-2, 2′-disulphonic acid stilbene, 500 μm) prevented buildup of Cl− current after a 30-min preincubation at 500 μm. When tested in a mitogenic assay, DIDS, flufenamic acid, NPPB and IAA-94 all inhibited T-cell proliferation, suggesting a physiological function in addition to the observed volume sensitivity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00232714

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