The Effects Of Arginine Levels On Casein Gene Expression Of Mammary Gland Epithelial Cell In Vitro From Dairy Cattle

Milk protein is a natural source of essential amino acids for humans and plays an important role in milk quality. Recently, the question of how to increase milk protein content has received more attention by animal scientists and nutritionists. Studies have shown that, the uptake of arginine by the ruminant mammary gland greatly exceeds its output in milk. Thus, we explored the potential effects of enhancing the local concentration of arginine in ruminant mammary cells as it relates to milk protein synthesis regulation.In this experiment, the Chinese Holstein cattle mammary epithelial cell was used as to assay the effects of arginine on casein synthesis. The experiment took Arg0-time group (0.00mg/L) as control, and Arg0.25-time group (69.50mg/L),0.5-time group (139.00mg/L),1-time group (278.00mg/L),2-time group (556.00mg/L),4-time group (1112.00mg/L),8-time group (2224.00mg/L) as treatment groups. The result showed that:(1) Compared with the control group, arginine adding can increase the growth of bovine mammary epithelial cells significantly (P<0.05).(2) Compared with other treatments, arginine adding at556.00mg/L level in culture medium had the best promotion efficiency on the expressions of a s-casein and β-casein in bovine mammary epithelial cells significantly (P<0.05).(3) Compared with other groups, arginine adding at556.00mg/L level had better promotion efficiency on the expressions of CS1N1, CS1N2, CSN2, CSN3gene significantly (P<0.05).(4) Among groups, the expression of JAK2, STAT5, mTOR and S6K gene was highest with Arg2-time group (P<0.05) containning556.00mg/L of arginine; the reverse was true for4EBP1gene, with the lowest expression in this group (P<0.05).(5) The cubic analysis showed that, arginine supplementation at a concentration range from369.65mg/L to729.64mg/L (1.3to2.6times) in culture medium, could stimulate casein synthesis in vitro.(6) Arginine also had some effects on arginine metabolic related enzymes activities. It was however that, the effects were different depending on different enzyme.Taken together, arginine with a certain range in culture medium have better promotion effect on casin expression in bovine mammary epithelial cells. Arginine appears to play an important role in the transcriptional regulation of casein genes, and furthermore arginine may affect casein expression through arginine related enzymes activities but can not tell in this work. More works are needed to be done to clarify in the future. Presently, our work has already clarified the casein expression rule and regulationry machnism, which can provide some basic information for milk quality increase.