The release of granule components from human polymorphonuclear leukocytes in response to both phagocytic and chemical...

The differential effects of phagocytic and chemical stimuli on neutrophil enzyme and specific protein release were compared. Phorbol myristate acetate (PMA) stimulated release of the specific granule matrix marker, vitamin B-12-binding protein in a dose-dependent manner. Subcellular fractionation by sucrose density gradient centrifugation indicated that the residual vitamin B-12-binding protein is associated with the specific granule fraction. In contrast, neutral alpha-glucosidase and adenosine diphosphatase, associated with specific granule membranes, were not released by PMA. Subcellular fractionation studies suggest that fusion of the specific granule membrane and plasma membrane occurs, thus translocating the adenosine diphosphatase to the cell surface. The relevance of this finding to the possible role of nucleoside phosphatases in limiting platelet aggregation is discussed. Serum-treated zymosan particles also caused a selective release of vitamin B-12-binding protein from the specific granule without release of alpha-glucosidase and adenosine diphosphatase. Neither PMA nor opsonized zymosan caused significant release of azurophil, tertiary granule or cytosol marker enzymes.