Benomyl-induced aneuploidy in mouse oocytes

Benomyl (methyl-1-[butylcarbamoyl]-2-benzimidazole carbamate) is a plant fungicide which acts by inhibiting tubulin polymerization. It is also a carcinogen and a teratogen. A substantial number of reports consistently show that benomyl inhibits cellular division and induces numerical chromosome changes in somatic cells, while results from standard genotoxicity assays which measure mutations and structural chromosome aberrations are conflicting. To define further the genotoxic effects of benomyl and to demonstrate the utility of the in vivo mouse oocyte assay for detecting chemicals which induce numerical chromosome changes, we investigated the ability of benomyl to induce numerical and structural chromosome aberrations in mouse oocytes. Superovulated female ICR mice were administered benomyl by oral gavage and oocytes were collected 17 h later. The proportions (and percentages) of hyperploid oocytes were 1/309(0.3), 6/155(3.9), 38/229(16.6), 46/130(35.4), 60/215 (27.9), 42/143(29.4) for control, 500, 1000, 1500, 1750 and 2000 mg/kg respectively. No increase in structural aberrations was observed. These results demonstrate that benomyl specifically induces numerical chromosome changes in mouse oocytes.