Abstract
We have developed sensitive and rapid assays to investigate histamine synthesis (histidine decarboxylase activity) (HD) and degradation (histaminase activity) during specific allergen triggered histamine release. HD activity was determined in isolated mast cells and mixed human leukocytes using 2-14C histidine (50uM, 0.5uc) as substrate. Synthesized histamine was separated by thin layer chromatography on cellulose sheets and quantitated in cut sections of chromatograms by liquid scintillation spectrometry. In isolated mast cells (>98%pure) HD activity was linear for at least 6 hr. with an activity of 20ng histamine synthesized /106 mast cells/hr. Histaminase activity was determined by a similar thin layer chromatographic technique. The degradative products formed from the interaction of soluble cell sonicates and 2-14C histamine (8uM, 0.1uc) were quantitated by scintillation spectrometry. Histaminase activity was undetectable in “mononuclear cell fractions” (>98% lymphocytes, monocytes, basophils) but was present in a granulocyte fractions (>98% neutrophils and eosinophils) of human leukocytes. In granulocytes, histaminase activity was associated principally with eosinophils. In eosinophil-rich fractions (95% pure), histaminase activity was linear for at least 5 hr. with an activity of 50 pmol/5×106 eosinophils/hr. These data suggest that the human eosinophil may modulate the allergic response by neutralizing histamine during allergen stimulated histamine release.
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Zeiger, R., Colten, H. HISTAMINE METABOLISM IN CELLS OF THE ALLERGIC RESPONSE. Pediatr Res 8, 421 (1974). https://doi.org/10.1203/00006450-197404000-00488
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DOI: https://doi.org/10.1203/00006450-197404000-00488