Effects of Estrogen and Prolactin on Casein Synthesis of Bovine Mammary Epithelial Cells
JIN Yaya, LI Dabiao*, SUN Mei, MU Xiaojia, CAO Yue, HAO Yihong
In order to explore the effect of combined addition of estrogen and prolactin on the synthesis of casein in dairy BMECs (bovine mammary epithelial cells) and the mechanism of action, the research team conducted a combined addition experiment based on the optimal estrogen and prolactin concentration screened in the early stage. The total amount of estrogen and prolactin added is 300 ng/mL. According to the ratio of the two additions, they are divided into test group I (control group, no estrogen and prolactin), test group II (estrogen׃prolactin=5׃1), test group III (estrogen׃prolactin=2׃1) and test group IV (estrogen׃prolactin=1׃2). MTT method was used to detect cell proliferation; qRT-PCR method was used to detect casein synthesis, mTOR signaling pathway and JAK2-STAT5 signaling pathway related gene expression; Western blot method was used to detect the levels of α-casein and β-casein in cells. The results showed that compared with the control group, the test groups II, III, and IV significantly increased the proliferation rate of BMECs, and increased CSN1S1, CSN3, AMPK, PI3K, AKT, mTOR, eIF4E, JAK2, STAT5, ERβ and PRLR in BMECs. The test group III and test group IV significantly increased the gene expression level of CSN2 in BMECs (P<0.05). Compared with the control group, test groups II and IV significantly increased the expression of BMECs α-casein and β-casein (P<0.05), and the expression of α casein increased by 22.7% and 38.6%, respectively. The protein expression increased by 62.9% and 102.9%, respectively. The expression of β-casein in group III was significantly higher than that of the 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 combination of 100 ng/mL estrogen and 200 ng/mL prolactin in test group IV had the best effect on promoting the synthesis of BMECs casein.
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