As the main precursor for lactose synthesis, large amounts of glucose are required by lactating dairy cows. whereas fatty acid synthase, sterol regulatory element binding protein-1 and beta-1, 4-galactosyl transferase mRNA expression increased at 10 mmol/L and then decreased at 20 mmol/L. The content of lactose synthase increased with increasing concentration of glucose, with addition of highest value at 20 mmol/L of glucose. Moreover, the increased glucose concentration stimulated the activities of pyruvate kinase and glucose-6-phosphate dehydrogenase, and elevated the energy status of the BMEC. Therefore, it was deduced that after increasing glucose availability, the extra absorbed glucose was partitioned to entering the synthesis of milk fat and lactose by the regulation of the mRNA expression of key genes, promoting glucose metabolism by glycolysis and Rabbit Polyclonal to APOL1 pentose phosphate pathway as well as energy status. These results indicated that the sufficient availability of glucose in BMEC may promote glucose metabolism, and affect the synthesis of milk composition. Introduction As the main precursor for lactose synthesis, large amounts of glucose are required by lactating dairy cows. Compared with non-lactating dairy cows, the requirements of glucose are approximately fourfold greater in lactating cows . Milk yield greatly depends on mammary lactose synthesis due to its osmoregulatory property for mammary uptake of water. Lactating mammary gland can consume up to 85% of the circulating glucose . Thus, the availability of glucose to the mammary gland could be a potential regulator of milk yield. The metabolic products of glucose, such as ATP and NAPDH, are important factors in milk synthesis of dairy cows. The effects of infusions of different glucose levels on lactation performance and metabolic profiles have been extensively studied , . Some studies have confirmed that milk yield curvilinear increased and milk protein concentration linear increased with increasing glucose levels , , whereas other trials have shown inconsistent results. With glucose infusion, SCH 530348 distributor Lemosquet et al.  and Al-Trad et al.  demonstrated no effect on milk yield, while Oldick et al.  observed a decrease in milk yield. These conflicting results may be ascribed to the inhibition or reduction of gluconeogenesis during glucose infusion , or the difference of diets providing post-ruminal supply of starch , . However, little information is available on the effects and not clear what mechanisms would be for glucose availability in bovine mammary epithelial cells (BMEC) Xiao and Cant found that at physiological glucose concentrations, phosphorylation by hexokinase (HK) exerts 80% of the control of glucose metabolism SCH 530348 distributor to lactose and CO2, and transport exerts the remaining 20% . Our previous study further revealed that glucose concentration affects glucose uptake partly by altering the activity of HKs, and HK2 may play an important role in the regulation of glucose uptake in BMEC . In the present study, BMEC were used to investigate the effect of glucose availability on expression of the key genes involved in synthesis of milk fat, lactose and glucose metabolism was determined by JC-1 (5, 5, 6, 6 – tetrachloro – 1, 1, 3, 3 – tetraethylbenzimidazolcarbocyanine iodide) method (Kaiji, Nanjing, China). Cells with a higher can absorb more JC-1 into the mitochondria to form polymers, which can be visualized by fluorescence microscopy at 550C620 nm (Nikon, Tokyo, Japan). The content of ATP was measured by the luciferin-luciferase method . Cells were lysed and cleared by centrifugation at 4C (12,000 g, 5 min), followed by the measurement of the luminescence in a luminometer (Molecular Devices, California, USA). Statistic Analysis Experiments were performed with four replicates, and each experiment was repeated three times. All data were statistically analyzed by ANOVA, and Duncans multiple range tests using the SAS software system. and ATP levels were observed in BMEC incubated with 10 mmol/L glucose than those incubated with 2.5 mmol/L glucose (and affected SCH 530348 distributor energy-dependent cell proliferation of.