Determination of gene mutations and cytogenetic damage in B{sub 6}C{sub 3}F{sub 1} Big Blue{reg_sign} mice treated with benzo(a)pyrene (BP), N-ethyl-N-nitrosourea (ENU), and N-nitrosodimethylamine (NDMA)

Transgenic rodents harboring easily recoverable shuttle vectors offer the prospect of studying gene mutations in vivo in any tissue of interest. The value of these models in genetic toxicology could be enhanced by evaluating a cytogenetic and point for chromosomal mutations from the same treated animals. The utility of such an approach is being evaluated in our laboratory by determining the frequencies of lac I mutations and micronuclei in B{sub 6}C{sub 3}F{sub 1} Big Blue{reg_sign} mice treated with known genotoxic agents. Groups of 12-week old male mice (4/group) were administered 3 daily oral doses of BP (250 mg/kg/day), ENU 50 mg/kg ENU on Days 1, 2, and 3, respectively. The last group was intended to optimize and probability of detecting gene mutations in various tissues from the same treated animals (to serve as potential positive control treatment in future studies). Forty eight hours after the last dose, peripheral blood was collected from the tail vein and wedge smears were prepared for the evaluation of micronucleated erythrocytes. After an expression period of 21 days (only 11 days for NDMA-treated animals due to toxicity), various tissues were collected, flash-frozen in liquid nitrogen, and stored at approximately -80{degrees}C for the analysis of lacImore » mutations. The incidence of micronucleated polychromatic erythrocytes were substantially elevated in all the treatment groups (25-, 29-, 12-, and 36-fold increase in groups treated with BP, ENU, NDMA, and the combination treatment, respectively). Analysis for lacI mutations in the DNA extracted from the livers indicated increases of approximately 9-, 4-, 7-, and 7-fold in groups treated with BP, ENU, NDMA, and the combination treatment, respectively (control frequency = 27 x 10{sup -6}). These data will be used for development of protocols for the simultaneous evaluation of chromosomal as well as gene mutation end points.« less