Regulation of histamine release from human basophil leucocytes: Role of H1, H2 and H3 receptors

A novel class of histamine receptors (H₃), controlling histamine synthesis and release, was described in rat and human brain and peripheral nerve endings. The present study was undertaken to evaluate whether H₃ receptors contribute to the regulation of histamine release from human basophils. Basophil leucocytes were incubated with a H₃ antagonist (thioperamide; concentrations ranging from 1 nM to 10 μM) or with a H₃ agonist ((R)αmethyl-histamine; concentrations ranging from 1 to 100 nM), and subsequently were stimulated with optimal doses of anti-IgE and formyl-methionyl-leucyl-phenyl-alanine (f-met peptide). No significant modifications of histamine release were observed after incubation either with the H₃ agonist or with the H₃ antagonist. By contrast, a H₂ antagonist (cimetidine; concentrations ranging from 1 to 100 μM) exerted a dose-dependent enhancing effect on anti-IgE- and, to a lesser extent, on f-met peptide-induced histamine release. A H₁ antihistamine (chlorpheniramine; concentrations ranging from 100 nM to 1 μM), at the highest concentration employed, displayed an inhibitory activity on IgE-dependent and IgE-independent histamine release. Exogenous histamine was shown to exert a dose-dependent inhibitory effect on two-staged anti-IgE-induced histamine release. Taken as a whole, these results suggest that H₃ receptors are not involved in the regulation of histamine release from human basophils; by contrast, H₂ receptors participate in controlling histamine release from human basophils, as previously demonstrated by other authors.