Journal of Leukocyte Biology 48:7-14 (1990) © 1990 Wiley-Liss, Inc. Stimulated Platelets Release Factor(s) Affecting the In

The metabolic and functional responses of human polymorphonuclear cells (PMNs) to thrombin-activated platelet supernatants were studied. The incubation of PMNs with su-pernatants from stimulated platelets (SPS) caused a 50 % decrease in both killing of Staphylococcus aureus and luminol-enhanced chemiluminescence (CL) by PMNs stim-ulated by opsonized-zymosan (OZ), Concanavalin A (Con A), or calcium ionophore A23187. The levels of PMN intracellular fluorescence measured by flow cytometry, using the fluorochrome dichlorofluorescin diacetate (DCF-DA), were considerably less in the presence of SPS than in resting platelet supernatants (RPS). No influence of platelet supernatant on 02 consumption and 02 generation by OZ-activated PMNs was ob-served. The incubation of PMNs with SPS caused a significant increase in the rate of chemotaxis and aggregation elicited by Con A, OZ, and phorbol myristate acetate (PMA). The supernatant from resting platelets did not show any of the above-reported effects. Platelets previously degranulated by thrombin were unable to inhibit CL when activated with agonists. Studies on the differential release of the granules by platelets showed that the CL-quenching activity paralleled the discharge of lysosomal content. The release of myeloperoxidase (MPO) from PMNs elicited by OZ was reduced in the presence of SPS. The platelet supernatant did not affect the MPO activity if PMNs were lysed with Triton X-100. The leakage of lactate dehydrogenase (LDH) from platelets was less than 3%, and no catalase or superoxide dismutase was released. This activity withstood lyophilization, but was destroyed by 10 mm heating at 100#{176}Cor by treatment with proteolytic enzymes. Key words: neutrophils, oxidative metabolism, platelet functio