Effects Of Estrogen And Prolactin On Casein Synthesis In Bovine Mammary Epithelial Cells

The aim of this study was to determine the appropriate level of estrogen(E2)and prolactin(PRL)for improving casein synthesis in bovine mammary epithelial cells(BMECs),so as to provide a theoretical basis for the regulation of milk composition synthesis.This thesis includes three experiments.In experiment 1,the effect of different level of E2(0,50,100,200,400 ng/m L)on casein synthesis of BMECs was investigated.The results showed that: Compared with the control group,adding 100 and 200 ng/m L E2 significantly increased the proliferation rate of BMECs(P<0.05).Adding 50 ng/m L E2 significantly increased the gene expression of CSN3,e IF4 E,GLUT8 and GLUT12(P<0.05);100 and 200 ng/m L estrogen significantly up-regulated the gene expressions of CSN1S1,CSN3,AMPK,m TOR,S6K1,e IF4 E,JAK2,STAT5,GLUT1,GLUT8,GLUT12,ERα,ERβ and PRLR(P<0.05).However,400 ng/m L E2 significantly down-regulated the gene expressions of AMPK,PI3 K and JAK2.Comprehensive consideration the results of proliferation rate and m RNA expression of casein gene,100 ng/m L E2 was the best level for improving casein synthesis of BMECs.In experiment 2,the effect of different levels of PRL(0,100,200,400,800 ng/m L)on casein synthesis of BMECs was investigated.The results showed that: Compared with the control group,adding 100 ng/m L and 200 ng/m L PRL significantly increased the proliferation rate of BMECs(P<0.05),while 400 and 800 ng/m L PRL had no significant effect on the proliferation rate of BMECs(P>0.05).100 ng/m L and 200 ng/m L PRL significantly up-regulated the gene expression of CSN1S1,CSN2,CSN3,AMPK,AKT,m TOR,S6K1,JAK2 and GLUT1 in BMECs(P<0.05).200 ng/m L PRL also significantly up-regulated the gene expression of e IF4 E,ERα,PRLR and GLUT8(P<0.05.400 ng/m L PRL significantly up-regulated the gene expression of CSN2,AMPK,AKT,S6K1 and ERβ,PRLR,GLUT1,GLUT8 and GLUT12(P<0.05).When the concentration of PRL reached800 ng/ml,the gene expressions of CSN3 and e IF4 E were significantly decreased(P<0.05).Adding 100 ng/m L and 200 ng/m L PRL significantly increased BMECs α casein and βcasein expression,and 200 ng/m L PRL group was the best.Based on the concentration of E2 and PRL selected by the previous two experiment,combined addition experiment 3 was carried out.The total supplementation amount of E2 and PRL was 300 ng/m L.According to the ratio of E2 to PRL,experiment were divided into test group I(control group,no supplementation of E2 and PRL),test group II(E2:PRL=5: 1),test group III(E2: PRL=2: 1)and test group IV(E2: PRL=1:2).The effect of combined adding E2 and PRL on the casein synthesis of BMECs was studied.The results showed that compared with the control group,the test group II,III and IV significantly increased the proliferation rate of BMECs,and increased the gene expression of CSN1S1,CSN3,AMPK,PI3 K,AKT,m TOR,e IF4 E,JAK2,STAT5,ERβ,PRLR,GLUT1,GLUT8 and GLUT12(P<0.05).Test group III and test group IV significantly increased the gene expression of CSN2 in BMECs(P<0.05).As compared with the control group,the test group II and IV significantly increased the expression of BMECs α casein and β casein(P<0.05),and the expression of α casein expression increased by 22.7% and 38.6%respectively,β casein expression increased by 62.9% and 102.9%,respectively.The expression of β-casein in group III was significantly higher than control group(P<0.05),while the expression of α-casein was not significantly different from that of the control group.Based on the results of cell proliferation and casein expression,the combined supplementationof 100 ng/m L E2 and 200 ng/m L PRL(test group IV)was the best level for promoting the casein synthesis of BMECs.