Binding of histamine-albumin conjugates to human lymphocytes: evidence for labelling of histamine H-1 but not H-2 receptors.
Histamine conjugated to human serum albumin (HSA) bound to a major proportion of human peripheral blood lymphocytes in a rosetting assay. In contrast, red cells coated with the control conjugates pentylamine-HSA and ethanolamine-HSA were unreactive. Amine conjugation by the carbodiimide method imposed a positive charge on the albumin molecule. However, the percentage histamine-HSA-binding lymphocytes was related to the amount of histamine coupled to the albumin molecule and not to differences in isoelectric point (pI) of the modified protein carriers. Four different histamine-albumin conjugates and one pentylamine-HSA conjugate inhibited lymphocyte binding of histamine-HSA, whereas ethanolamine-albumin, carbodiimide-reacted HSA and native albumin were not inhibitory. The histamine H-2 receptor antagonists cimetidine, ranitidine, metiamide, and burimamide lacked inhibitory effects. The histamine H-1 receptor antagonists clemastine, mepyramine, and diphenhydramine efficiently inhibited lymphocyte binding of the histamine-albumin conjugate with IC50 values of 0.2, 1, and 40 mM, respectively, indicating interactions with low affinity H-1 receptors.
Department of Medical Microbiology, Lund University, Sweden.
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T
Hallberg
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M
Dohlsten
D001667:Binding, Competitive; D006632:Histamine / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism*; D011968:Receptors, Histamine / Q000378:metabolism*; D011969:Receptors, Histamine H1 / Q000378:metabolism*; D011970:Receptors, Histamine H2 / Q000378:metabolism*; D012709:Serum Albumin / Q000378:metabolism*
D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D012709:Serum Albumin; D006632:Histamine