Study On Anabolism Of The Main Components Of Milk In Cow Mammary Gland

Mammary gland is a unique organ in mammals. Its function is lactation. Mammary gland undergoes a series of changes in morphology and structure.These changes are closely related to material metabolism in mammary gland which directly affect the quality and product of milk. There are very a few substance metabolism studies on the development of mammalian mammary gland in different period, especially dairy cow.Genes of four caseins and two whey proteins were detected by using fluorescent quantitative RT-PCR in different developmental periods of mammary gland. The results showed that all genes were up-regulated in lactation period. The expression of PRLR, AKT1, STAT5, ELF5, EIF4BP1、 S6K which may relate to protein metabolism in mammary gland were detected, the results showed that other genes had the same expression tendency with milk proteins genes expect EIF4EBP1. It implied that they involved in processes of transcription or translation of milk proteins. Down-regulation of EIF4EBP1demonstrated its negative roles in lactation. PRLR regulated the transcription of milk proteins by the activation of STAT5from JAK2. AKT1played important roles at the level of translation of milk proteins through the negative regulation of mTOR on EIF4EBP1and positive regulation of mTOR on S6K.β-casein was first appeared at6month in pregnancy in cow mammary gland.Some genes were chosen from different aspects in lipid metabolism to detect their mRNA levels by fluorescent quantitative RT-PCR. They included:VLDLR, LPL which related to the uptake of fatty acid. FABP3, ACBP which related to the transport of fatty acid in cell.ABCA1, ABCG2which related to the transport of foreign cholesterol. Activation of ACSL1, ACSS2, ACSS1. ACACA, FAS which related to the fatty acid de novo synthesis. SCD, FADS1, FADS2which related to desaturation. AGPAT6, GPAM, LPIN, DGAT1, DGAT2which related to the synthesis of triacylglycerol. BTNlA1, XDH, ADFP which related to the synthesis of lipid droplet. PPARG, SREBF1and SREBF2which related to transcriptional regulation. The results showed that these genes expressed in mammary gland epithelium appeared up-regulated in lactation period. SREBP1and SREBP2and PPARG were located in the centre of the lipid metabolism regulation.The Regulation of PRLR、AKT1to lipid metabolism in diary cow mammary gland was realized through regulation of SREBP1.C16:0, C18:0and C18:1contents were higher than the other fatty acids in cow milk. Technology of fluorescent quantitative RT-PCR was used to detect the mRNA expression of HK Ⅰ, HKⅡ, GLUT1, LALBA and β-1,4-galactosyl transferase in different period of dairy cow mammary gland. The results showed that mRNA expression of these genes were increased and large of lactose was synthesized in mammary gland of cows during the whole lactation. LALBA and β-1,4-galactosyl transferase were the key enzyme that catalysis lactose. HPLC was chosen to detect the lactose in mamary gland to determine the time point of lactose synthesis and its production. Lactose appeared until6month in pregnancy in mammary gland.The expression and the localization of glucose transporter-1(GLUT1) were detected in different period of dairy cow mammary gland by Western blotting and laser scanning confocal microscopy. The results showed that the expression of GLUT1protein are similar to the expression of GLUT1mRNA in different period of dairy cow mammary gland. In virgin, the expression of GLUT1mRNA and GLUT1protein was lowest and increased during pregnancy. On140day of lactation, the expression of GLUT1mRNA and GLUT1protein reached the highest levels and remained high levels during the whole lactation. In involution, the expression of GLUT1mRNA and GLUT1protein was decresaed because of apoptosis of mammary epithelial cells. In virgin and early pregnancy, GLUT1was found in ductal epithelial cells; in late pregnancy and lactation, GLUT1was detected in alveolus epithelial cells near to the basal lamina and epiphragm.These results showed that GLUT1could taransfer extracellular glucose into cells to provide enerage and substance for mammary gland development and lactation.