RESUMEN
The effect of alveolar macrophages (AM) harvested from Wistar rats by lung lavage on proliferation of human embryo pulmonary fibroblasts in culture was investigated. It was observed that supernatants of AM decreased the uptake of (3)H TdR by the pulmonary fibroblasts. The AM activated with opsonized zymosan (OPZ) showed a stronger inhibitory effect on fibroblast proliferation compared with inactivated AM. Following pretreatment with indomethacin, the inhibitory effect of AM was abolished and reversed to stimulatory effect on pulmonary fibroblast proliferation. The PGE content in AM supernatant was measured with radioimmunoassay. It was observed that the inhibitory effect of AM was highly correlated to prostaglandin (PGE) content in the supernatant of AM. The results suggest that AM has both inhibitory and stimulatory effects on the proliferation of pulmonary fibroblast; the inhibitory effect is primary under normal conditions. This inhibitory action is mainly due to PGE secreted from AM. It is, therefore, suggested that AM plays an important role in suppressing pulmonary fibrosis under normal conditions.