A comparative study on the protective effects of 17beta-estradiol, biochanin A and bisphenol A on mammary gland differentiation and tumorigenesis in rats.

Mammary tissue differentiation and tumorigenesis were studied in female rats following subcutaneous injection at 2, 4 and 6 days after birth with low or high doses of 17beta-estradiol (0.1 or 10 microg; E2), biochanin A (0.1 or 10 mg; BCA) or bisphenol A (0.1 or 10.0 mg; BPA). Half of the rats were killed on day 35 to analyze the terminal end bud (TEB), terminal duct (TD) and alveolar bud (AB) of the mammary tissue. The remaining rats were injected, ip, with a dose of 50 mg/kg of N-nitroso-N-methylurea (MNU) at 7 weeks of age and sacrificed 26 weeks later. The incidence and multiplicity of mammary tumors (MT) decreased among all three different treated groups, dose-dependently. However, the pattern of mammary gland differentiation varied. No significant difference was observed after E2 administration. TEB decreased dose-dependently in BCA treated groups and the number of TD and AB were suppressed significantly in BPA high dose group.

Tumorigenesis in infant C3H/HeN mice exposed to tritiated water (HTO).

The purpose of this study was to determine the carcinogenicity and retention of tritiated water (HTO) in mice. A two-part study was undertaken. In an HTO-incorporation study, both sexes of 12-day old C3H/HeN mice were i.p. injected with 3.70 MBq/pup of HTO and sacrificed 3 hr and 1, 3, 7, 14 days after HTO administration; in a carcinogenicity study, pups were given a single i.p. injection of HTO at doses of 0, 0.23, 0.92 and 3.70 MBq/mouse, and then observed for 14 months. The survival rates of both sexes slightly decreased upon increasing the HTO administered doses. The results indicated that the administration of HTO to infants led to a significant increase of liver tumors in male mice, but not in females. In female mice, ovarian tumors were observed for the high-dose group of injected HTO.