Voltage-dependent ion channels on human basophils: do they exist?
The presence of voltage-dependent ion channels (particularly Ca2+ channels) on the surface of 'non excitable' cells such as human basophils is a matter of debate. Indeed, in basophils, Ca2+ entry or mobilization is not sufficient by itself to trigger secretion, although enhanced cytosolic Ca2+ concentration increases it. In order to address this question, we used a two-signal model and we report here experiments which suggest the presence of voltage-dependent structures directly or indirectly linked to membrane Ca2+ pathways. Indeed, it is known that, in the presence of PMA at threshold concentration (1st signal), elevation of cytosolic Ca2+ (2nd signal) induces histamine release. We observed that a depolarizing external solution (high K+) induced a Ca(2+)-dependent release of histamine from PMA-treated human basophils. High K+ alone did not induce histamine release. Although the voltage-sensitive component and the physiological relevance of this mechanism remain to be defined, these results suggest that this voltage-dependent Ca2+ influx in the human basophil could contribute to the up-regulation of histamine release.
Beauvais
F
F
INSERM U200, Université Paris-Sud, Clamart, France.
Burtin
C
C
Benveniste
J
J
D001491:Basophils / Q000737:chemistry*; D015220:Calcium Channels / Q000276:immunology; D006636:Histamine Release; D006801:Humans; D015640:Ion Channel Gating / Q000276:immunology*; D007473:Ion Channels / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology
D015220:Calcium Channels; D007473:Ion Channels