title: Membrane depolarization selectively inhibits receptor-operated calcium channels in human T (Jurkat) lymphoblasts.
abstract: Jurkat lymphoblasts were stimulated by a monoclonal antibody against the CD3 membrane antigen and the evoked calcium signal was followed by the intracellular fluorescent calcium indicator indo-1. The technique applied allowed us to separately investigate the stimulus-induced intracellular calcium release and the calcium-influx pathways, respectively. In the same cells membrane potential was estimated by the fluorescent dye diS-C3-(5). The resting membrane potential of Jurkat lymphoblasts under normal conditions was between -55 and -60 mV. Membrane depolarization, obtained by increasing external K+ concentration, removing external Cl-, or by increasing the Na+/K+ leak permeability with gramicidin or PCMBS, did not induce calcium influx in the resting cells and did not influence the CD3 receptor-mediated internal calcium release, while strongly inhibited the receptor-mediated calcium influx pathway. Half-maximum inhibition of this calcium influx was observed at membrane potential values of about -35 to -40 mV and this inhibition did not depend on the external calcium concentration varied between 5 and 2500 microM. Membrane hyperpolarization by valinomycin did not affect either component of the calcium signal. The observed selective inhibition of the receptor-operated calcium influx pathway by membrane depolarization is probably an important modulator of calcium-dependent cell stimulation.
authors.affiliation: National Institute of Haematology and Blood Transfusion, Budapest, Hungary.
authors.forename: B
authors.initials: B
authors.lastname: Sarkadi
authors.forename: A
authors.initials: A
authors.lastname: Tordai
authors.forename: G
authors.initials: G
authors.lastname: Gárdos
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D005456:Fluorescent Dyes; D006801:Humans; D007211:Indoles; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D015398:Signal Transduction; D013601:T-Lymphocytes
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015220:Calcium Channels; D005456:Fluorescent Dyes; D007211:Indoles; D011948:Receptors, Antigen, T-Cell; D002731:4-Chloromercuribenzenesulfonate; C048960:indo-1; D002118:Calcium