Effects of DMBA preparation on DMBA-induced rat mammary carcinogenesis

We compared two protocols for 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis. DMBA (20 mg/ml) was prepared at room temperature or at 60degreesC and administered by gavage to 50-day-old Sprague-Dawley rats. Two days post-DMBA, mammary epithelial DNA was P-32-postlabeled. At 12 weeks post-DMBA, tumor DNA was screened for H-ras codon 61 mutations using an enriched polymerase chain reaction (EPCR). The number of in situ carcinomas (3.0 +/- 2.7 vs. 2.5 +/- 2.7), invasive carcitionias (1.1 +/- 1.6 vs, 0.6 +/- 0.8), and H-ras codon 61 mutations (34 +/- 13% vs. 23 +/- 13%) were statistically not different (p = 0.05) between the groups. The relative adduct levels in mammary organoids were significantly (p < 0.001) greater in the 60degreesC (568 158) than the room temperature (150 130) group. While DMBA-DNA adduct levels differed significantly between these protocols, this did not correlate with significant differences in tumor pathologies or H-ras codon 61 mutations.