Regulation of human basophil activation. IV. Dissociation between cationic dye binding and histamine release: role of Ca2+ ions.
In previous studies we observed that in vitro histamine release from human basophils could be dissociated from the loss of affinity of basophil granules for a cationic dye, toluidine blue. In the present study we further explored the intracellular signals leading to the decrease in toluidine blue positive basophil (TB+) numbers, with or without histamine release. Since Ca2+ mobilization is a crucial event in secretion and particularly in histamine release, we studied the role of Ca2+ in histamine release as compared to TB+ decrease. In the presence of external Ca2+ (2 mM): i) Ca2+ channel antagonists verapamil and nifedipine up to 10 microM were without effect on IgE-mediated histamine release and TB+ decrease; ii) loading of the leucocytes with Quin2 or preincubation with TMP-8, an internal Ca2+ antagonist, significantly inhibited the release of histamine and the decrease of TB+ basophils. In the absence of added external Ca2+:i) histamine release was abolished whereas the decrease of TB+ was not modified, even in the presence of EGTA;ii) the decrease of TB+ could be inhibited by prolonged EGTA preincubation, by Quin2 loading and incubation with TMB-8. We conclude that histamine release requires both external Ca2+ influx and mobilization of internal Ca2+. In contrast, no influx of external Ca2+ is required for TB+ decrease in which, however, internal Ca2+ mobilization appears to play an important role.
Beauvais
F
F
INSERM U. 200, Université Paris-Sud, Clamart, France.
Hiéblot
C
C
Burtin
C
C
Benveniste
J
J
D000888:Antibodies, Anti-Idiotypic / Q000502:physiology; D001491:Basophils / Q000187:drug effects*; D002118:Calcium / Q000502:physiology*; D006636:Histamine Release / Q000187:drug effects*; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D015290:Second Messenger Systems / Q000187:drug effects; D014048:Tolonium Chloride / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
D000888:Antibodies, Anti-Idiotypic; C026408:anti-IgE antibodies; D014048:Tolonium Chloride; D007073:Immunoglobulin E; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium