Lactoferrin is an estrogen responsive protein in the uterus of mice and rats

To identify lactoferrin (LF) and determine its estrogen-responsiveness in t he rat uterus, immature Sprague-Dawley rats were untreated or subcutaneousl y injected with 17 beta-estradiol (500 mu g/kg) for 3 days and uterine tiss ues collected. Outbred immature CD-1 mice, treated with 17 beta-estradiol, provided the positive control. By using a polyclonal antibody raised agains t mouse LF, minimal detectable protein was immunolocalized in uterine epith elial cells of untreated immature rats and mice. After estrogen treatment, LF was localized in all uterine epithelial cells of both species, although staining was more intense in mice than rats. In mice, LF was evenly distrib uted throughout the cytoplasm with intense staining in some cells, while in rats, it was seen mainly in the apical cytoplasm. For comparison to anothe r well-known estrogen responsive protein in rats, complement C3 was immunol ocalized within epithelial cells and it showed a different staining pattern than LF. Uterine tissue homogenates were analyzed by sodium dodecyl sulfat e-polyacrylamide gel electrophoresis and Western blots showed cross-reactiv ity with the mouse LF antibody. These findings indicate that LF is present in the rat uterus, and is induced by estrogens as reported in other species . Thus, LF is an important marker of estrogenic activity across species and will, therefore, have utility in screening for effects of environmental es trogenic compounds. Published by Elsevier Science Inc.