VOLTAGE-DEPENDENT ION CHANNELS ON HUMAN BASOPHILS - DO THEY EXIST

The presence of voltage-dependent ion channels (particularly Ca2+ chan nels) on the surface of 'non excitable' cells such as human basophils is a matter of debate. Indeed, in basophils, Ca2+ entry or mobilizatio n is not sufficient by itself to trigger secretion, although enhanced cytosolic Ca2+ concentration increases it. In order to address this qu estion, we used a two-signal model and we report here experiments whic h suggest the presence of voltage-dependent structures directly or ind irectly linked to membrane Ca2+ pathways. Indeed, it is known that, in the presence of PMA at threshold concentration (1st signal), elevatio n of cytosolic Ca2+ (2nd signal) induces histamine release. We observe d that a depolarizing external solution (high K+) induced a Ca2+-depen dent release of histamine from PMA/treated human basophils. High K+ al one did not induce histamine release. Although the voltage-sensitive c omponent and the physiological relevance of this mechanism remain to b e defined, these results suggest that this voltage-dependent Ca2+ infl ux in the human basophil could contribute to the up-regulation of hist amine release.