Lactotransferrin gene expression in the mouse uterus and mammary gland.

The mouse mammary gland and uterus expressed the gene for the secretory protein lactotransferrin under various physiological conditions. Lactotransferrin, however, was induced by estrogen in a time- and dose-dependent fashion in the uterus of the immature mouse, but was not affected by estrogen in the mammary gland. Differences were also found in the expression of lactotransferrin in mammary glands and uteri of adult females during lactation. A high level of the protein was detected by immunocytochemistry in uterine epithelial cells 1 day after parturition, but immunoreactivity disappeared quickly thereafter. Lactotransferrin message was, however, relatively abundant in the mammary gland at the end of the lactation period. The presence of lactotransferrin in various tissues also was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Two forms of immunoreactive material was detected by this method; a 70K band was found in uterine luminal fluid from the estrogen-stimulated immature mouse and in homogenates of lung, vagina, mammary gland, oviduct, spleen, lymph node, and uterus of the adult female mouse, and a 65K band was detected in submaxillary gland, kidney, ovary, and all of the above tissues. Brain and duodenum had no detectable immunoreactive material. A transient appearance of lactotransferrin was observed in the uterine luminal fluid of pseudopregnant mice. These changes in the level of lactotransferrin in the uterus and mammary gland under various physiological conditions suggest that the regulation of this protein's expression is tissue specific.