Ontogeny of lactoferrin in the developing mouse uterus: a marker of early hormone response

Lactoferrin (LF) was mapped during organogenesis of the murine reproductive tract, starting on fetal Day 12, as a marker of estrogen responsiveness. To induce LF expression, pregnant outbred CD-1 mice were injected s.c. with diethylstilbestrol (DES; 100 microg/kg maternal body weight), and fetal genital tract tissues were removed; neonatal and immature mice received s.c. injections of DES (2 microg/pup per day). Corn oil-treated and untreated mice at corresponding ages provided the controls. Immunocytochemical techniques using a polyclonal antibody showed no detectable LF in control genital tract tissues until late gestation. However, after DES treatment, LF was localized in uterine epithelial cells as early as fetal Day 14; the intensity of LF staining increased with age and number of DES treatments. Control uterine tissues responded to the rise of circulating estrogens at parturition (fetal Day 19) by producing LF, although the magnitude of response was lower than that of DES-treated tissues. Uterine tissue homogenates from control and DES mice were analyzed by SDS-PAGE and Western blots, verifying the protein to be LF. Isolation of mRNA and Northern blot analysis further showed that LF mRNA was present in the developing Mullerian duct and that DES stimulated early induction of the LF gene. The early appearance of LF suggests that it may play an important role in the hormonal regulation of growth and differentiation of developing uterine tissues.