We examined the effect of scavengers of reactive oxygen metabolites on proteinuria in the passive Heymann nephritis model of membranous nephropathy. Passive Heymann nephritis was induced by a single intravenous injection of anti-Fx1A IgG in a dose of 10 mg/100 g body weight. Superoxide dismutase, a scavenger of superoxide or catalase which destroys hydrogen peroxide, did not affect the proteinuria. In contrast, dimethylthiourea (DMTU, 500 mg/kg followed by 125 mg/kg ip twice a day), a scavenger of hydroxyl radical, markedly reduced the proteinuria (day 5: anti-Fx1A 53 +/- 13, n = 18; anti-Fx1A + DMTU, 21 +/- 6 mg/24 h, n = 15, P less than 0.001). Experiments with 125I-labeled anti-Fx1A antibody demonstrated that DMTU did not affect the amount of antibody deposited in the kidney. Semiquantitative estimation of IgG and complement deposition in the kidney showed no differences between the DMTU-treated and control rats. A second hydroxyl radical scavenger, sodium benzoate (150 mg/kg ip twice a day), also resulted in marked reduction in proteinuria (day 5: anti-Fx1A 56 +/- 7, n = 9; anti-Fx1A + benzoate, 14 +/- 4 mg/24 h, n = 8, P less than 0.01). Because of the participation of iron in biological systems to generate hydroxyl radical, we also examined the effect of deferoxamine (DFO, 35 mg/day), an iron chelator, on the anti-Fx1A-induced proteinuria. There was a significant reduction in proteinuria in rats treated concurrently with DFO (day 5: anti-Fx1A 67 +/- 13, n = 15; anti-Fx1A + DFO, 29 +/- 4 mg/24 h, n = 15, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)