Glucose is universal and essential fuel of energy metabolism and in the synthesis pathways of all mammalian cells. Glucose is the one of the major precursors of lactose synthesis using glycolysis result in producing milk fat and protein. During the milk fat synthesis, lipoprotein lipase (LPL) and CD36 are required for glucose uptake. Various morecules such as acyl-CoA synthetase 1 (ACSL1) activity of acetyl-CoA synthetase 2 (ACSS2), ACACA, FASN AGPAT6, GPAM, LPIN1 are closely related with milk fat synthesis. Additionally, glucose plays a major role for synthesizing lactose. Activations of lactose synthesize enzymes such as membranebound enzyme, beta-1,4-galactosyl transferase (B4GALT), glucose-6-phosphate dehydrogenase (G6PD) are changed by concentration of glucose in blood resulting change of amount of lactose production. Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. There are 2 types of glucose transporters which consisted facilitative glucose transporters (GLUT); and sodium-dependent transport, mediated by the Na+/glucose cotransporters (SGLT). Among them, GLUT1, GLUT8, GLUT12, SGLT1, SGLT2 are main glucose transporters which involved in mammary gland development and milk synthesis. However, more studies are required for revealing clear mechanism and function of other unknown genes and transporters. Therefore, understanding of the mechanisms of glucose usage and its regulation in mammary gland is very essential for enhancing the glucose utilization in the mammary gland and improving dairy productivity and efficiency.

A cell frequently utilizes glucose as a fuel of energy and a major substrate of lipid and protein syntheses. A regulation of glucose movement into and out of the cells is precisely controlled by cooperative works of passive and sodium‐dependent active processes. At least 13 glucose cotransporter (Slc2a, GLUT) isoforms involve in passive movement of glucose in cells. The efferent ductules (EDs) play in a number of important functions for maintenance of male fertility. In the present study, using real‐time PCR analysis, we determined gene expression of five Slc2a isoforms in the EDs. In addition, we compared expression levels of these Slc2a isoforms according to postnatal development ages, 1 week, 2 weeks, 1 month, and 3 months. Results from the current study showed that expression of Slc2a1, Slc2a3, and Slc2a5 mRNAs reached the highest levels at 1 month of age, followed by a transient decrease at 3 months of age. In addition, the level of Slc2a4 mRNA reminded at steady until 1 month of age and was significantly reduced at 3 months of age, whereas the highest level of Slc2a 8 mRNA was detected at 2 weeks of age. Data from the present study indicate a differential expression of various Slc2a isoforms in the ED according to postnatal ages. Thus, it is believed that glucose movement through the epithelial cells in the ED would be regulated by the coordinated manner among Slc2a isoforms expressed at a given age.

이온 비의존적으로 작동하는 포도당 수송체 (glucose transporter 1, Glut1)는 생쥐 배아의 세포막을 경계로 포도당을 수송하는 주요통로이다. 성장인자 가운데 insulin-like growth factor-I (IGF-I)은 생쥐배아에서 포도당의 유입을 증가시키는 것으로 알려져있으나 이러한 효과가 IGF-I 의한 Glut1의 전사조절 효과에 기인한 것인지는 알려져 있지 않다. 본 연구는 포도당과 IGF-I 생쥐의 착상전 배아 발생과 G