Transmembrane ion conductance in human B lymphocyte activation.
Human B lymphocytes were examined to determine whether transmembrane ion conductance plays a role in cell activation. Mitogens (anti-human IgM F(ab')2 fragment (anti-mu) and PMA) were used to stimulate B lymphocytes. Mitogen-induced DNA synthesis was inhibited by tetraethylammonium-Cl (TEA), 4-aminopyridine (4AP), verapamil, and diltiazem in a dose-dependent manner. This inhibition was not due to reduction in cell viability as determined by trypan blue exclusion. Mitogen-induced increases in RNA synthesis were partially inhibited by TEA and 4AP and were more completely inhibited by verapamil and diltiazem. Mitogen-induced cell volume increases were not affected by TEA or 4AP but were completely inhibited by verapamil and diltiazem. B lymphocytes stimulated with anti-mu expressed G1 phase cell surface antigens in the presence of TEA or 4AP, but failed to do so in the presence of verapamil or diltiazem. Substitution of PMA for anti-mu as the mitogen did not alter the effects of TEA or 4AP. However, verapamil inhibited PMA-induced expression of G1 phase cell surface markers although diltiazem did not. The patch clamp technique was used to directly examine plasma membrane ionic currents in whole-cell, cell-attached, and inside-out patch configurations. Activation of B lymphocytes with either anti-mu or the Ca2+ ionophore, A23187, inhibited opening of one type of channel in cell-attached patches. In inside-out patches, this channel type conducted current when the bath [Ca2+] was low (6 X 10(-8) M) but failed to conduct current when the bath [Ca2+] was increased above 1 X 10(-6) M. The results of these experiments are consistent with the hypothesis that activation of B lymphocytes induces alterations in plasma membrane ion conductance. Single channel studies suggest that activation induced increases in [Ca2+]i may directly inhibit a specific set of plasma membrane ion channels as one mechanism by which transmembrane ion flux is altered.
Department of Pediatrics, University of Alabama, Birmingham 35294.
L H
LH
Brent
J L
JL
Butler
W T
WT
Woods
J K
JK
Bubien
D015761:4-Aminopyridine / Q000494:pharmacology; D001402:B-Lymphocytes / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects; D004110:Diltiazem / Q000494:pharmacology; D004553:Electric Conductivity; D006801:Humans; D007148:Immunoglobulin mu-Chains; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008213:Lymphocyte Activation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D015221:Potassium Channels / Q000502:physiology; D011947:Receptors, Antigen, B-Cell / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D007148:Immunoglobulin mu-Chains; D007473:Ion Channels; D015221:Potassium Channels; D011947:Receptors, Antigen, B-Cell; D013757:Tetraethylammonium Compounds; D000001:Calcimycin; D015761:4-Aminopyridine; D014700:Verapamil; D004110:Diltiazem; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium