The importance of proteoglycans for secretionof proteolytic enzymes was studied in the murine macrophage cell line J774. Untreated or 4b-phorbol 12-myristate 13-acetate (PMA)-stimulated macrophages were treated with hexyl-b-D-thioxyloside to interfere with the attachment of glycosaminoglycan chains to their respective protein cores. Activation of the J774 macrophages with PMA resulted in increased secretion of trypsin-like serine proteinase activity.