title: Immunoglobulin E receptor-activated calcium conductance in rat mast cells.
abstract: 1. The nystatin perforated-patch method was used to record macroscopic currents from anti-trinitrophenyl (TNP) immunoglobulin E (IgE)-sensitized rat basophilic leukaemia (RBL-2H3) cells at 37 degrees C. 2. An inwardly rectifying Ca2+ current (ICa) was activated upon stimulation with the multivalent antigen trinitrophenylated bovine serum albumin (TNP-BSA). Induction of ICa was not observed at room temperature. ICa was reversed and reinduced upon cyclical addition of the monovalent hapten dinitrophenyl (DNP)-lysine and multivalent antigen, indicating that a specific interaction of antigen with IgE was required to elicit ICa. 3. The antigen-induced current was also carried by Ba2+ or Sr2+, and to a lesser extent by Na+, in the nominal absence of Ca2+. ICa did not exhibit time-dependent opening (< or = 1 ms) in response to hyperpolarizing voltage steps to -100 mV, although it did accumulate steady-state inactivation of approximately 40-50% over 100 ms. 4. Two inorganic blockers of antigen-stimulated 45Ca2+ influx and secretion, La3+ and Zn2+, inhibited ICa by approximately 50% at concentrations known to produce 50% block of 45Ca2+ influx. In contrast, cromolyn sodium (0.5 mM) and the L-type Ca2+ channel antagonist nitrendipine (5 microM) had no effect on ICa. 5. ICa also was induced by the intracellular Ca2+ mobilizer thapsigargin. Because the actions of thapsigargin and antigen were not additive, IgE receptor cross-linkage appears to activate the recently described capacitative Ca2+ entry channels.
authors.affiliation: Department of Zoology and Genetics, Iowa State University, Ames 50011-3223, USA.
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: M A
authors.initials: MA
authors.lastname: McCloskey
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D004205:Cromolyn Sodium / Q000494:pharmacology; D006241:Haptens / Q000276:immunology; D007073:Immunoglobulin E / Q000276:immunology / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology; D008407:Mast Cells / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D009568:Nitrendipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013324:Strontium / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014407:Tumor Cells, Cultured
chemical_list: D000941:Antigens; D015220:Calcium Channels; D006241:Haptens; D017455:Receptors, IgE; D013729:Terpenes; D001464:Barium; D007073:Immunoglobulin E; D019284:Thapsigargin; D007811:Lanthanum; D009568:Nitrendipine; D012964:Sodium; D004205:Cromolyn Sodium; D002118:Calcium; D013324:Strontium