Failure of N-acetylcysteine to protect the mouse bone marrow against the clastogenicity of 7,12-dimethylbenzanthracene.

De Flora et al. (1991a) have demonstrated a marked protective effect afforded by N-acetylcysteine (NAC) to the liver and lung of rats exposed to benzo[a]pyrene (BP) by intratracheal injection. Due to the protocol used by De Flora et al., BP was inactive in the bone marrow micronucleus assay and, consequently, the possible protective effect of NAC in this tissue could not be assessed. In the present study, three daily administrations of 7,12-dimethylbenzanthracene (DMBA; 15 or 25 mg/kg/day via oral gavage) resulted in the expected increased in micronucleated polychromatic erythrocytes (MPE) in the bone marrow of male C57BL/6 mice 24 h after the final dose. Pretreatment of similar groups of mice with NAC (1 g/kg/day via oral gavage) 5 h before each administration of DMBA had no effect on MPE frequencies. It is concluded that NAC does not have a protective effect on the mouse bone marrow.