Hepatic microsomal enzymes in Schistosoma mansoni-infected mice: I. Effect of duration of infection and lindane administration on dimethylnitrosamine demethylases.

The prevalence of schistosomiasis in Egypt, its suspected relationship to carcinoma of the bladder, and the inevitable exposure of schistosomal patients to insecticides prompted the undertaking of this study. Dimethylnitrosamine (DMN) demethylases, responsible for the activation of DMN, were assessed in the hepatic microsomes from albino mice under the influence of Schistosoma mansoni infection and/or lindane administration. DMN-demethylase I responded to infection by an early increase in activity, reaching a peak 30 days after disease induction and declining sharply afterwards. DMN-demethylase II followed the same general pattern, but it reached its peak 20 days after infection and declined at a slower rate than DMN-demethylase I. The effects of lindane, an organochlorine insecticide, were also studied on these two enzymes in uninfected mice and in S. mansoni-infected animals after different durations of disease induction. Given orally, in a dose of 40 mg/kg/day for 3 consecutive days, lindane increased the activity of both enzymes. Since DMN requires metabolic activation for its hepatotoxic and carcinogenic actions, alterations in its activating enzymes, as a consequence to schistosomiasis and/or exposure to lindane, may change susceptibility to its toxic and carcinogenic potentials.