Expression And Function Of Leptin And Its Receptor In Mammary Gland Of Mouse

Leptin was a cytokine which was synthesized and secreted by body fat. It was also produced by mammary fat pad and mammary epithelial cells through paracrine and autocrine. Leptin controlled the development and lactation of mammary gland. It influenced the development of duct in virgin and stimulated the proliferation of mammary epithelial cells. At present, the research about leptin and the long form of leptin receptor (OB-Rb) was only the expression of them in mRNA and the impact of leptin on the proliferation of mammary epithelial cells in culture. There were no results about the expression of leptin and OB-Rb in protein and the impacts of leptin on the development, lactation and involution of mammary gland. It was also not clear about the signal transduction pathway of leptin in mammary gland.In these experiments, for the first time, we investigated the expression and localization of leptin and OB-Rb in protein which were produced by mouse mammary gland itself in virgin, pregnancy, lactation and involution systematically by Confocal laser scanning microscope. These results showed that in virgin, the expression of leptin was highest and degraded at the beginning of pregnancy. On pregnancy 16d, the expression of leptin in mammary gland upgraded slightly then degraded and kept at the low level during the whole lactation. In involution, mammary epithelial cells were apoptosis and adipose tissue restored again, the expression of leptin increased and recovered to the original level about virgin on involution 13d. In the whole development cycle, the expression of OB-Rb was similar with leptin and showed significant positive correlation. This indicated that the expression of leptin induced the expression of OB-Rb positively in development, lactation and involution mammary gland. In virgin and early pregnancy, leptin was found in adipocytes, ductal epithelial cells and basal lamina around the duct and OB-Rb was found in adipocytes and ductal epithelial cells; in late pregnancy and lactation, leptin was detected in alveolus epithelial cells near to the basal lamina and extracellular matrix, OB-Rb was detected on the membrane of alveolus epithelial cells near to the basal lamina; in involution, mammary fat pad restored and leptin was existed in adipocytes and ductal epithelial cells again and OB-Rb was also existed in adipocytes and ductal epithelial cells.The localization of leptin and OB-Rb were similar suggested that in each development period of mammary gland, leptin affected the development and physiology function of mammary gland by binding OB-Rb.In order to clarify the biological function of leptin and OB-Rb in the development cycle of mammary gland, explants of mammary gland were cultured in a synthetic medium with various...