Autoradiographic Study of the Effects of Estrogen on in vivo Incorporation of 3H-Uridine into Uterine Smooth Muscle and Stromal RNA in the Aging

An autoradiographic study was made ofde novo RNA synthesis and nuclear area in endometrial stroma and myometrium in ovariectomized C57B1/6J mice. A comparison of uterine tissue from young adult (4 to 7 month old) mice was made with tissue from animals at the age of decreased fertility (15 months of age). In mice receiving exogenous estradiol-17/3 there was an age related decrease in nuclear grain counts 60 min after injection of 3H-uridine which was more pronounced in endometrial stroma than in myometria when mice were compared with oil injected controls of the same age. The mean nuclear area of both cell types was greater in estrogenized mice than in control mice. The decrease in endometrial stromal response to exogenous estrogen is consistent with, and may contribute to, decreasing fertility with advancing maternal age. R EPRODUCTIVE decline with advancingmaternal age is manifested by a decrease in the frequency and size of litters in poly-tocous species. Previous reports from our laboratory indicate that there is a decreasing responsiveness to ovarian steroid hormones in uterine tissue which occurs in C57B1/6J mice at an age when there is no concomitant decrease in the number of eggs ovulated or their viability. Harman and Talbert (1970) found no age related decrease in ovulation by 15 months of age in this strain but did note a decrease in the number of implantation sites by seven days post-coitum at 11 months of age. Shapiro and Talbert (1974) reported a decrease in mechanically induced deciduoma formation by 11 months of age as compared to younger animals. Estrogen has been shown to have early effects on uterine RNA synthesis (Gorski et al., 1965; Hamilton et al., 1968), water imbitio