Lack of Modifying Effects of Combined Treatment of t-butylhydroquinone and Sodium Nitrite on Forestomach Carcinogenesis in rasH2 Mice Initiated with N-ethyl-N-nitrosourea

In order to examine the modifying effects of co-administration of t-butylhydroquinone (TBHQ) and sodium nitrite (NaNO2) on forestomach carcinogenesis, a total of 50 male transgenic mice carrying a human prototype c-Ha-ras gene (rasH2 mice) received a single intraperitoneal injection of 60 mg/kg body weight of N-ethyl-N-nitrosourea (ENU), and starting 1 week later, they were given diet containing 0 (control group) or 0.5% TBHQ (TBHQ alone group), drinking water containing 0.2% NaNO2 (NaNO2 alone group) or diet containing 0.5% TBHQ in combination with 0.2% NaNO2 in drinking water (TBHQ+NaNO2 group) for 20 weeks. Squamous cell hyperplasias, papillomas and carcinomas were induced in all of the ENU treated groups, and there were no significant differences in the incidence, multiplicity and PCNA labeling index of these forestomach proliferative lesions between the NaNO2 alone, TBHQ alone, TBHQ+NaNO2 and control groups. These results suggest that the co-administration of TBHQ and NaNO2 does not cause any modifying effects on ENU-induced forestomach carcinogenesis in rasH2 mice.