Substance Metabolism Of Dairy Goat Mammary Gland

Mammary gland has the ability to change nutrients into milk composition. Mammary gland epithelial cells is called as a"biological factory"for this. Lactation is the major function of mammry gland. Mammalian has exclusive function of lactation, when the ability is activated mammalian could provide food nutrition equilibrium for growth and development to neonatal progenies in different strains. This function relates to the special development of mamary galnd. Development of mammary gland completed almost in adulthood. It is regulated by hormones and growth factors complicated.Substance metabolism of mammary gland is essential for its development and lactation. In this research, three aspects which included precursors in serum, key enzymes and transfer proteins in mammary gland and products in milk were chose to research the sustance metabolism of carbohydrates, lipids and proteins systematically. The research was devoted to study the changes of substance metabolism in process of mammary gland development and lactation especially. The relationships of these changes were also noticed.Mammary gland can not synthesis glucose by itself, it can uptake glucose from serum by special transfer proteins to supply the energy and substance consumption in lactation. To research glucose metabolism fluorescent quantitative RT-PCR was used to study the mRNA expression of AKT1, PRLR, HKⅠ, HKⅡ, GLUT1, GLUT4, GLUT12, LALBA andβ-1, 4-galactosyl transferase in different development and lactation phases of mammary gland.Immunofluorescence histochemistry and Western blotting analysis were used to study the location of GLUT4 and its expression of protein level in mammary gland respectively. HPLC was chose to detect the lactose in mamary gland and milk to determine the time point of lactose synthesis and its production. Results showed that the expressions of AKT1, PRLR, HKⅠ, HKⅡ, GLUT1, GLUT12, LALBA andβ-1, 4-galactosyl transferase mRNA up-regulated in lactation period, the expression of GLUT4 down-regulated in lactation period. Lactose appeared at P150d in mammary gland. To research the lipid metabolism in mammary gland some genes were chose from different aspects in lipid metabolism to detect their mRNA levels by fluorescent quantitative RT-PCR. They included: VLDLR, LPL, CD36 which related to the uptake of fatty acid. ABCA1, ABCG2 which related to the transport of foreign cholesterol. FABP3, FABP4, ACBP which related to the transport of fatty acid in cell. Activation of ACSL1, ACSS2, ACSS1. ACACA, FAS which related to the fatty acid de novo synthesis. SCD, FADS1, FADS2 which related to desaturation. AGPAT6, GPAM, LPIN, DGAT1, DGAT2 which related to the synthesis of triacylglycerol. BTN1A1, XDH, ADFP, PLIN which related to the formation of lipid droplets. BDH1 and OXCT1 which related to the using of ketone body. INSIG1, INSIG2, SCAP, PPARG, PPARGC1A, PPARGC1B, THRSP, SREBF1 and SREBF2 which related to transcriptional regulation. SPTLC2, LASS2, SGPL1, UGCG, OSBP and OSBP10 which related to the synthesis of sphingolipid. Results showed that most of genes expressed in mammary gland epithelium appeared up-regulated in pregnancy and lactation period. Some genes expressed in adipocytes appeared down-regulated in development may because of fatty resignation. According the results of genes detected a draft of metaboliam network for fat synthesis in dairy goat mammary gland was finished. C16:0, C18:1n9c and C18:1n9t contents were higher than the other fatty acids in goat milk.In the research of protein metabolism, genes of four caseins and four whey proteins in different developmental periods were detected. The results showed all genes up-regulated in lactation period. The expression of lactoferrin mRNA increased dramatically in early lactation.The expression of PRLR, AKT1, STAT5, ELF5, EIF4BP1,S6Kinase and Caveolin1 mRNA which may related to protein metabolism in mammary gland were detected, the results showed that expect CAV1 and EIF4E-BP1 other genes had the same expression tendency with milk proteins. It implied that they involved in processes of transcription or translation of milk proteins. Down-regulation of CAV1 and EIF4E-BP1 demonstrated their negative roles in mammary gland. Genes of milk proteins were all up-regulated in lactation. The level of lactoferrin mRNA got peak value in L1d. The result implyed that lactoferrin gene plays an important role in secretory activation. PRLR regulates the transcription of milk proteins by the activation of STAT5 from JAK2. AKT1 regulates the translation of milk proteins by the regulation of mTOR to EIF4E-BP1 and S6K.β-casein was first appeared at P90d in goat mammary gland.