title: Resting and activation-dependent ion channels in human mast cells.
abstract: The mechanism of mediator secretion from mast cells in disease is likely to include modulation of ion channel activity. Several distinct Ca(2+), K(+), and Cl(-) conductances have been identified in rodent mast cells, but there are no data on human mast cells. We have used the whole-cell variant of the patch clamp technique to characterize for the first time macroscopic ion currents in purified human lung mast cells and human peripheral blood-derived mast cells at rest and following IgE-dependent activation. The majority of both mast cell types were electrically silent at rest with a resting membrane potential of around 0 mV. Following IgE-dependent activation, >90% of human peripheral blood-derived mast cells responded within 2 min with the development of a Ca(2+)-activated K(+) current exhibiting weak inward rectification, which polarized the cells to around -40 mV and a smaller outwardly rectifying Ca(2+)-independent Cl(-) conductance. Human lung mast cells showed more heterogeneity in their response to anti-IgE, with Ca(2+)-activated K(+) currents and Ca(2+)-independent Cl(-) currents developing in approximately 50% of cells. In both cell types, the K(+) current was blocked reversibly by charybdotoxin, which along with its electrophysiological properties suggests it is carried by a channel similar to the intermediate conductance Ca(2+)-activated K(+) channel. Charybdotoxin did not consistently attenuate histamine or leukotriene C(4) release, indicating that the Ca(2+)-activated K(+) current may enhance, but is not essential for, the release of these mediators.
authors.affiliation: Division of Respiratory Medicine, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: S M
authors.initials: SM
authors.lastname: Duffy
authors.forename: W J
authors.initials: WJ
authors.lastname: Lawley
authors.forename: E C
authors.initials: EC
authors.lastname: Conley
authors.forename: P
authors.initials: P
authors.lastname: Bradding
mesh_terms: D000328:Adult; D001773:Blood Cells / Q000276:immunology; D015550:Cell Degranulation; D004553:Electric Conductivity; D005312:Fetal Blood; D006636:Histamine Release; D006801:Humans; D007073:Immunoglobulin E; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology*; D017997:Leukotriene C4 / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000276:immunology; D008407:Mast Cells / Q000276:immunology*; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*
chemical_list: D007473:Ion Channels; D024681:Potassium Channels, Calcium-Activated; D017997:Leukotriene C4; D007073:Immunoglobulin E