Increase in collagen content of lung post-bleomycin in gp91phox-/- but not in MM12-gp91phox double knockout mice. Total collagen content freshly synthesized in lung was measured by Sircol assay. Data represent mean of 2 independent experiments, n = 4/group. Data are expressed as avergae ± SEM. *P < 0.05 compared to the post-OVA value in wildtype mice. Abbreviations: WS, saline-treated wildtype (baseline); WB, bleomycin-treated (single intra-tracheal dose of 0.075 U/ml bleomycin and animals were sacrificed 14 and 21 d later. Here day 21 data are shown); NOXS, saline-treated gp91phox null; NOXB, bleomycin-treated gp91phox null; DKOS, saline treated MMP12- gp91phox double knockout; DKOB, bleomycin-treated MMP12- gp91phox double knockout.