Direct action of estradiol on rat mammary tumors

To demonstrate a direct effect of estrogen on the growth of 7,12 dimethylbenz[a]anthracene (DMBA) induced rat mammary tumors, the authors studied the in vitro incorporation of ³H leucine by the tumors. Tumor tissue obtained from ovariectomized rats was incubated at 37°C for 2 hr under 95% oxygen and 5% carbon dioxide in a chemically defined medium containing 0.5 μCi/ml ³H leucine. The addition of 0.1 μg/ml 17β estradiol to the incubation medium increased the incorporation of radioactivity into tumor protein by 7%. This increase was statistically significant (P<0.001). It is concluded that estrogen directly stimulates protein synthesis in the mammary tumors.