Mutagenicity of o-anisidine to the bladder of lacI– transgenic B6C3F1 mice: absence of 14C or 32P bladder DNA adduction

Earlier studies have established that the rodent bladder carcinogen o-anisidine (OA) gives negative results in all of the standard rodent genetic toxicity assays. In the present study, a single oral administration of the maximum tolerated dose level (750 mg/kg) of OA to B6C3F1 mice yielded negative results in 32 P-post-labelling assays of bladder and liver DNA (24 h after dosing). Likewise, 14 C-ring-labelled OA administered orally to B6C3F1 mice gave no evidence of DNA binding 6, 12 or 24 h later. Administration of OA (750 mg/kg) to transgenic lacI - mice (Big Blue) led to a small increase in mutation frequency (MF) in the bladder, but not in the liver