The effect of various doses (0-10 mg/kg body wt.) of teniposide (VM-26) was studied on the induction of micronuclei at 12, 24 and 36 h post-treatment. The frequency of micronuclei (MPCE and MNCE) increased in a dose-dependent manner up to a dose of 0.3125 mg/kg VM-26, where a peak frequency of micronuclei was observed. A further increase in the drug dose resulted in the reduction in micronuclei frequency in comparison with 0.3125 mg/kg drug dose reaching a nadir at 10 mg/kg. However, it was significantly higher than DDW (double distilled water) treated controls. The pattern of micronuclei induction was similar for all the post-treatment time periods. The frequency of micronuclei also increased with scoring time and the highest frequency of micronuclei was observed at 24 h post-treatment, which declined thereafter without restoration to DDW treated control level. Conversely, the PCE/NCE ratio registered a dose-dependent decline after treatment of mice with various doses of VM-26. A peak decline was observed at a dose of 0.3125 mg/kg, thereafter the decline became consistently less resulting in an elevation in the PCE/NCE ratio in comparison with 0.3125 mg/kg VM-26. Copyright (C) 1999 Elsevier Science Ireland Ltd.
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