Temporal and cell-type specific expression of c-fos and c-jun protooncogenes in the mouse uterus after estrogen stimulation

Employing immunohistochemistry and in situ hybridization, we studied the temporal and cell type specific localization of c-Fos and c-Jun proteins and the corresponding messenger RNAs (mRNAs) elicited by a single 17β-estradiol (E₂) injection in the uteri of castrated adult mice. Cellular expression of mRNAs was in parallel with the synthesis of proteins within 1 h, E₂ stimulated the c-fos expression rapidly and transiently in the epithelium and vascular endothelium. A second small peak of c-Fos protein and c-fos mRNA expression occurred around 11-13 h in the epithelium. No detectable amount of c-fos transcript and protein was present throughout the time course (0-24 h) in the stromal and myometrial cells. E₂ treatment caused differential c-jun expression in all uterine cell types. In the epithelium, c-jun mRNA and protein expression was decreased during 1-6 h post injection, and thereafter returned showing small peak around 11-13 h. Induction of c-Jun protein and c- jun mRNA was evident in the stromal and myometrial cells at 2-3 h, and then the expression gradually decreased and returned to nearly control level by 24 h. E₂ treatment induced rapid and transient activation of c-jun in the vascular endothelium. Present results suggest that transient increase of c- Fos and decrease of c-Jun protein at the early phase and coexpression of these proteins at the late phase contribute the proliferation of endometrial epithelium in mature mice. Furthermore, c-Fos and c-Jun expression in the vascular endothelium at the early phase may participate in the uterine inhibition.