A large, multiple-conductance chloride channel in normal human T lymphocytes

Abstract

Chloride (Cl) channels have been proposed to play roles in lymphocyte functions including volume regulation and cellular cytotoxicity; however, direct studies of such channels in normal human lymphocytes are lacking. In the present study we describe a large conductance Cl channel observed in about 50% of excised, inside-out patches from normal human peripheral T lymphocytes. The channel has multiple conductance states with linear single-channel current-versus-voltage relationships in symmetrical Cl solutions. The most prevalent state is the largest, which has a conductance of about 365 pS. The channel closes in a voltage-dependent manner at both negative and positive potentials, but does not show voltage-dependent inactivation. The probability of opening is maximal between -15 mV and +15 mV and the voltage dependence is well described by two Boltzmann equations with half-maximal probabilities at -22.8 mV and +18.0 mV. The slopes of the voltage dependence suggest two gates in series with 5.7 and 9.6 equivalent charges. The channel was about 30 times more selective for Cl- than for Na+ or K+ under balanced osmolarity but less selective (approx. 11:1) under a large osmotic gradient. The single-channel conductance increased with Cl concentration with an apparent saturation at about 581 pS and a Michaelis-Menten constant of about 120 mM. The selectivity sequence among anions, determined from changes in reversal potential was: I- greater than NO3- greater than Br-, Cl- greater than F-, isethionate, HCO3- greater than SO4(2-) greater than gluconate, propionate greater than aspartate much greater than Na+, K+ and was apparently the same for subconductance states.(ABSTRACT TRUNCATED AT 250 WORDS)

High conductance anion channel in Schwann cell vesicles from rat spinal roots

“…This issue was not further explored in the present study. The blocking effect of zinc is in accordance with the pharmacological activity of this ion on high conductance anion channels in other tissues (Schlichter et al, 1990;Woll et al, 1987). Therefore, zinc might be a pharmacological tool to study these channels.…”

The maxi-anion channel: a classical channel playing novel roles through an unidentified molecular entity

“…3c). The halfmaximal open probability (V 1/2 ) was observed at -22.8 and ?18 mV in normal T lymphocytes with effective gating charges of 5.7 and 9.6 for negative and positive voltages, respectively [104]. In cultured L6 myoblasts, the V 1/2 values were -25.6 and ?49.6 mV for quiescent cells and -15.5 and ?31.4 mV for rapidly proliferating cells [24].…”

“…Resembling maxi-anion channels were also found in fibroblasts [14,66,[88][89][90][91][92] and endothelial cells [93][94][95][96][97]. In the immune system, the maxi-anion channel activity has been confirmed in B lymphocytes [98][99][100][101], in T lymphocytes [102][103][104] and in peritoneal macrophages [17,105]. In other tissues, mast cells [106], keratinocytes [107], osteogenic cells [108], cultured glomus cells of the carotid body [109], PC12 pheochromocytoma cells [110], pavement cells from the gills of the trout [111] and mammary gland C127 cells [8,11,112] have also been shown to possess this channel.…”

“…Most authors noted that the maxi-anion channel has multiple subconductance states of various levels, such as *15, *50, *100, *150 and *200 pS [2,17,29,95]. When the ambient Cl -concentration varied, the single-channel conductance saturated at 640 pS with K m = 112 mM in L6 myoblasts [24], at 581 pS with K m = 120 mM in T lymphocytes [104] and at 617 pS with K m = 77 mM in frog skeletal muscle ''sarcoballs'' [113].…”

Calcium‐dependent chloride current induced by axotomy in rat sympathetic neurons.

“…The Nernst equation predicts a reversal potential of +33 mV in the low Cl-solution. These discrepancies could be due to partial permeability of chloride channels to other ions (Hussy, 1992) or to isethionate (Schlichter, Grygorczyk, Pahapill & Grygorczyk, 1990) and to uncertainties on the assessment of junction potentials, especially in the sucrose solution (see Methods). Nevertheless, the results agree with the IADP being carried by Cl-ions.…”