Effect of cyclosporin A on the membrane potential and Ca2+ level of human lymphoid cell lines and mouse thymocytes.
The effect of the immunosuppressive cyclosporin A (CsA) on the cytosolic free Ca2+ concentration ([Ca2+]i) and membrane potential of human B and T lymphoblastoid cells and mouse thymocytes was studied in order to reveal some features of the early stage of drug-cell interaction. Cytosolic free Ca2+ concentration of the cells was measured by spectrofluorimetry using indo-1 and quin2 fluorescent calcium indicators. Membrane potential was monitored in a flow cytometer with oxonol dye. CsA applied at 2-20 micrograms/ml final concentrations caused a dose-dependent, rapid, transient rise of [Ca2+]i in all cell types. This effect could be blocked by chelating the extracellular Ca2+ with EGTA but was not sensitive to Ca2+ channel blockers verapamil and nifedipine or K+ channel blocker 4-aminopyridine. A possible explanation for the calcium mobilizing effect of CsA is an ionophore-like mode of action at the cell membrane level. Besides directly interfering with mitogenic signals, the elevation of [Ca2+]i could be responsible for an initial hyperpolarization observed in CsA-treated T lymphocytes. This hyperpolarization, however, was not detectable in B lymphoblastoid cells. A further difference between B and T cells was the diverse pattern of depolarization following CsA treatment. This variance in the behaviour of T and B lymphocytes and the diversity of membrane transport systems in its background could account for the different final outcome of the drug-cell interaction.
Department of Biophysics, University Medical School of Debrecen, Hungary.
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G
Vereb
G
G
Panyi
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M
Balázs
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L
Mátyus
J
J
Matkó
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S
Damjanovich
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D003524:Cyclosporins / Q000494:pharmacology*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*
D003524:Cyclosporins; D002118:Calcium