Abstract
The rate of in vitro metabolism of dimethylnitrosamine (DMNA) in liver cell preparations from rats given ip injections of DDT (50 mg/kg every second day for two, four, or eight doses) or a single ip injection of 3-methylcholanthrene (100 mg/kg) was compared with the rate of preparations obtained from control rats. The activity of O-demethylase in liver postmitochondrial supernatant was measured as an overall indicator of microsomal enzyme induction. Treatment of rats with DDT two or four times or with 3-methylcholanthrene caused only slight enhancement of the DMNA metabolism rate. Significant differences were observed after eightfold DDT administration. O-Demethylase activity was significantly different among all treated groups, and activity in all treated groups was significantly different from that of the controls. However, there was no correlation between the DMNA metabolism rate and the O-demethylase activity. In vivo studies were carried out to measure the rate of the DMNA disappearance from the blood of rats treated with DDT in the same manner as in the in vitro experiment. DMNA was administered ip to rats at 40 mg/kg 24 hr after the last dose of DDT. No DMNA was detected in the blood of the DDT-induced rats 8 hr after it was injected.
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