STRAIN DIFFERENCES IN THE ONTOGENY OF ESTROGEN-RECEPTORS IN MURINE UTERINE EPITHELIUM

The expression of estrogen receptor (ER) in the reproductive tracts of neonatal mice was examined using im-munocytochemical and autoradiographic methods. Two strains of mice used in previous studies that reported contradictory results showed different rates of uterine epithelial development. In the inbred strain, BALB/c, the epithelium was devoid of receptor from birth through 5 days of age, while uterine epithelial cells of the outbred strain, CD-I, expressed ER as early as 3 days of age. Oviductal epithelium and cervical epithelium expressed ER on the day of birth in CD-I mice. Glandular ontogeny in the uteri of CD-I animals was also advanced by 3 days compared to that of BALB/c mice. These observations reconcile the conflicting reports of ER ontogeny in the neonatal mouse. Moreimportantly, these results confirm our earlier observations, indicating that the cells lining uteri of 2-and 4-day-old BALB/c mice lack ER at a time when estrogen induces their proliferation. © 1990 by The Endocrine Society.