Polymorphonuclear neutrophils release 35S‐labelled proteoglycans into cartilage during frustrated phagocytosis

Rabbit peritoneal polymorphonuclear neutrophils (PMN), incubated in medium containing [35S]sulphate, incorporated 35S into proteoglycan and protein fractions. Approximately 46% of the 35S‐labelled macromolecules associated with the PMN cells after 1 h of incubation were recovered in a cytoplasmic granule extract, the majority being present in azurophil granules. Analysis of the azurophil granule fraction showed that approximately 90% of the 35S‐labelled macromolecules were proteoglycans. When challenged with heat‐aggregated rabbit γ‐globulin in the presence of cytochalasin B and cGMP, PMN were induced to release granular enzymes but did not release 35S‐labelled proteoglycans into the incubation medium. When incubated with articular cartilage slices, PMN released their granule 35S‐labelled proteoglycan into the medium and into the cartilage matrix. Granule enzymes and 35S‐labelled granule proteoglycan were extracted from the cartilage tissue after incubation and 35S‐labelled macromolecules were detected in the cartilage tissue by autoradiography.