Inhibition of DNA synthesis by retinyl acetate during chemically induced mammary carcinogenesis.

The effect of retinoids on DNA synthesis was studied in the female Sprague-Dawley rat. Animals were treated with either solvent, 7,12-dimethylbenz(a)anthracene, or 1-methyl-1-nitro-sourea at 50 days of age and were placed on either placebo or retinyl acetate diet at 57 days of age. [3H]Thymidine incorporation into purified DNA isolated from mammary parenchymal cells was determined. Retinyl acetate effectively inhibited mammary cell DNA synthesis in both 1-methyl-1-nitrosourea- and 7,12-dimethylbenz(a)anthracene-treated animals; however, DNA synthesis in solvent-treated animals was unaffected.