Estrogen induces c-fos expression specifically in the luminal and glandular epithelia of adult rat uterus.

It was previously shown that injection of 17 beta-estradiol into adult ovariectomized rats induces a rapid and transient increase of c-fos gene transcription in the uterus. Immunohistochemical analysis now shows that estrogen activates c-fos specifically in the luminal and glandular epithelial cells of the endometrium, which are the only uterine cells responding to the hormone with DNA synthesis and cell proliferation, and not in estrogen receptor positive stromal and myometrial cells. This finding suggests that c-fos is involved in the mechanism of estrogen regulation of uterine epithelial cell proliferation and, furthermore, that the c-fos activation by estrogen is cell type dependent.