Macrophages and the synthesis of connective tissue components.

1. Macrophage homogenate, added to the incubation medium of granulation tissue slices, decreases the incorporation of labelled proline to collagen and other proteins, to a greater extent in the presence of certain prostaglandins and in oxygen atmosphere, but to a lesser degree if serotonin and cyclic AMP are added. 2. Rheumatoid synovial fluid, connective tissue active peptide (CTAP) of Castor and an extract from CCl4-damaged liver stimulate collagen synthesis in the presence of macrophages. 3. Preparations from non-treated macrophages stimulate the incorporation of glucosamine to acid mucopolysaccharides, mainly hyaluronate. 4. In a developing rat granuloma, the formation of collagen was stimulated by homogenized macrophages and by macrophage culture medium, but especially by whole macrophages in the presence of SiO2.