**4. Conclusion**

Mammals rely exclusively on milk supply from the mammary gland to survive at an early age. The proliferation of mammary epithelial cells and mammary establishment depend on glucose supply to the gland, whereas lactose synthesis depends directly on glucose entry into the Golgi of MEC, which is conjugated with UDPgalactose by lactose synthase to produce the disaccharide lactose. MEC presents polarized expression of GLUT1, SGLT1, and GLUT12 in its plasma membrane and also expresses GLUT1, GLUT8, and SGLT1 in the Golgi. Hormones and oxygen tension regulate the expression of these transporters; however, further studies are necessary to explore the effects of light/dark cycles and suckling in their expression, since these are factors involved in milk production. Additionally, the kinetics of transporters involved in glucose uptake in the Golgi or cytoplasm of MEC also needs to be explored. Understanding the regulation and function of glucose transporters will be useful to improve efficiency of milk yield in both, humans and cattle.
