Induction of arginase I and II in bleomycininduced fibrosis of mouse lung

drolyzes arginine to urea and ornithine, is a precursor for the synthesis of polyamines and proline, which is abundant in collagen. The supply of proline can be a crucial factor in the process of lung fibrosis. We investigated the induction of arginine metabolic enzymes in bleomycin-induced mouse lung fibrosis. Histological studies and quantification of lung hydroxyproline showed that lung fibrosis develops in up to 14 days after bleomycin treatment. Under these conditions, col-lagen I mRNA was induced gradually in up to 15 days, and the content of hydroxyproline reached a maximum at 10 days. Arginase I mRNA was undetectable before bleomycin treatment but was induced 5–10 days after this treatment. Arginase I protein was induced at 7 days and remained little changed for up to 10 days and decreased at 14 days. On the other hand, arginase II mRNA that was detectable befor