BLEOMYCIN-INDUCED ARTHRITIS AND DERMATITIS IN RATS

We investigated the effect of the antitumor drug bleomycin (BLM) on sy novial membrane and periarticular deep dermis in 10-wk-old young adult rats. BLM was found to induce edema, mononuclear cell infiltration an d necrosis of the synovial membrane in the knee and tarsal joint, and inflammation in the deep dermis of the plantar hindfoot and digital pu lvini in these rats after subcutaneous administration of 20 mg/kg for 3 days. After a 4-wk recovery period, foci of degenerative collagen bu ndles were observed in the deep dermis of the plantar hindfoot in spit e of complete recovery of the lesions in the other dermal and synovial membrane sites. The synovitis was determined to begin with vesiculati on of the macrophage-type lining cells, followed by edema and cell inf iltration, especially near ligament insertion sites in the knee joint. The early dermal lesion consisted of dissociation of endothelial and subendothelial cells in small blood vessels thought to be postcapillar y venules, edema, and monocyte infiltration. The severity of arthritis was greater in young adults than juvenile rats. From these results, B LM was shown to have a toxic effect on synovial lining cells and to in duce inflammation in the synovial membrane and periarticular dermis.