| Abstract: | The release of histaminase, a diamine oxidase of the human neutrophil, is initiated by soluble secretagogues. Histaminase is simultaneously inactivated by the reactive oxygen intermediates generated by the respiratory burst. Thus, quantitative assessment of histaminase release relative to other granule markers is best achieved in the presence of superoxide dismutase and catalase. Human neutrophils activated with secretagogues preferential for the specific granule, such as calcium ionophore A23187 in a limited concentration, phorbol myristate acetate (PMA), formyl-methionyl-leucylphenylalanine (fMLP), and concanavalin A, release vitamin B12-binding protein, lysozyme, and histaminase but not beta glucuronidase. PMA activation in the presence of cytochalasin B augments the release of lysozyme and initiates the release of beta glucuronidase through recruitment of the azurophilic granule but has no incremental effect on the release of vitamin B12-binding protein and histaminase observed with PMA alone. Subcellular fractionation of resting neutrophils by sucrose density gradient centrifugation to separate specific granules from two classes of azurophilic granules selectively distributes vitamin B12-binding protein and histaminase to the specific granule fractions. |
