The differential effects of estrogen and progesterone on the uterus of the ovariectomized golden hamster.

The effects of estrogen and progesterone on incorporation of 3H-thymidine by the uterus of the ovariectomized hamster are reported. In the ovariectomized hamster progesterone alone did not induce incorporation of 3H-thymidine. Estrogen alone caused significant incorporation of 3H-thymidine, predominantly in the luminal epithelium wheras a prior or subsequent treatment with progesterone activated DNA synthesis in the stroma and muscualris. These results indicate the role of estrogen in priming the uterus of the hamster for the subsequent action of progesterone.