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.