CYTOCHEMISTRY OF PLASMA MEMBRANES ACTIVATED BY PHORBOL MYRISTATE ACETATE AND CALCIUM IONOPHORE IN THE ALVEOLAR AND PERITONEAL MACROPHAGES OF GUINEA PIGS

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Ultrastructural H₂O₂ producing sites in guinea pig peritoneal (PM) and alveolar (AM) macrophages stimulated with soluble stimuli were studied using a cerium technique. Electron-dense deposits resulting from H₂O₂ and CeCl₃ reactions were observed on the contacted surface of aggregated PM plasma membranes stimulated by formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol myristate acetate (PMA). The AM stimulated by FMLP or PMA demonstrated no significant cell aggregation or H₂O₂ production. Although calcium ionophore A23187 did not induce any cell aggregation, deposit formation was apparent on the free surface of plasma membranes. These results indicate that cell-cell contact may have an important role in H₂O₂ production induced by FMLP and PMA, and that H₂O₂ production induced by A23187 may not depend on cell aggregation.