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 a fforded by N-acetylcysteine (NAC) to the liver and lung of rats expose d to benzo[a]pyrene (BP) by intratracheal injection. Due to the protoc ol used by De Flora et al., BP was inactive in the bone marrow micronu cleus assay and, consequently, the possible protective effect of NAC i n this tissue could not be assessed. In the present study, three daily administrations of 7,12-dimethylbenzathracene (DMBA; 15 or 25 mg/kg/d ay via oral gavage) resulted in the expected increase in micronucleate d 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 doe s not have a protective effect on the mouse bone marrow.