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Glucose transporter (GLUT) 4 is a major mediator of blood glucose levels and is a key regulator of whole-body glucose homeostasis.The objectives of this study were to evaluate the function of goat GLUT4 on glucose absorption and the effect of GLUT4 on lactose synthesis in goat mammary gland epithelial cells.In the current study, the cDNA of a putative facilitative glucose transporter, GLUT4, was cloned from goat.To investigate the function of goat GLUT4, we constructed the eukaryotic expression vector pcDNA3.1-GLUT4 and used it to transfect goat mammary gland epithelial (GMGE) cells, thus generating GLUT4 transfected goat mammary gland epithelial (G4T-GMGE) cells.Then, we transfected of pcDNA3.1-GLUT4 into Goat Mammary Gland Epithelial Cells, and detected the mTOR pathway gene expression.Glucose and lactose amylase was performed by Glucose Assay Kit and Lactose Assay Kit in the medium of the G4T-GMGE cells or GMGE cells.The deduced GLUT4 sequence comprised 509 amino acids, producing a putative protein with a molecular weight of approximately 55 kDa.Both glucose uptake and lactose synthesis were increased in the G4T-GMGE cells when compared with the GMGE cells.At the transcriptional level, GLUT4 expression was increased nearly 55-fold in the G4T-GMGE cells, and the expression of amino acid transporters (SLC1A5, SLC3A2 and SLC7A5) was similarly enhanced;in contrast, GLUT1 expression was decreased by more than 50% in the G4T-GMGE cells.These results suggest that goat GLUT4 functions in the transport of glucose and that it may play a positive role in amino acid uptake in mammary glands.