AUTORADIOGRAPHY OF MAMMARY-GLANDS AND UTERI OF MICE AND RATS AFTER INJECTION OF [ESTRADIOL-H-3]

The distribution of radioactivity in mammary glands and uteri of lactating mice and rats, and in mammary glands of pregnant rats was studied 1 h after the injection of [2,4,6,7-3H]-estradiol-17.beta., using drymount autoradiography. In mammary glands of lactating animals, radioactivity was concentrated in nuclei of epithelial cells of acini and duct, while myoepithelial cells and fat cells did not retain radioactivity. In the same animals the uterine tissues also showed nuclear concentration of radioactivity in stromal, glandular and muscle cells, with little or no concentration of radioactivity in luminal epithelial cells. In pregnant rats on day 7 and 13 a weak concentration of radioactivity was observed in epithelial cells of the acini and ducts of the mammary gland. The autoradiographic results demonstrate that certain tissues of the mammary gland are targets for estradiol, similar to the uterus.