| It is well known that mammary growth is a major determinant of milk yield capacity and longevity of lactation. In growing animals, either overfeeding or severely restricting total nutrient intake inhibits normal development of the mammary gland. There are very a few energy metabolism studies on the development of mammalian mammary gland in different period, especially dairy goats.In this research, activitives of key enzymes about energy metabolism in different period of dairy goat mammary gland were studied. The results showed that activitives of hexokinase (HK), isocitrate dehydrogenase (ICDH) and ATPase were increased at the beginning of pregnancy, and remains high leves during the whole lactation. On 35 day of lactation, activitives of HK, ICDH and ATPase reached the highest levels. In involution, activitives of these enzymes were decreased. The significant increase the activities of these enzymes indicated an upregulated energy metabolism in dairy goat mammary gland. Activities of CPT and G6PDH were increased at the beginning of lactation. On 35 day of lactation, activitives of carnitine palmitoyltransferase (CPT) and 6 - phosphogluconate dehydrogenase (G6PDH) was highest. In involution, these enzymes were degraded. The significant increase the activitiy of CPT indicates that the oxidation of fatty acids were increased during lactation.To investigate the adenylate pool and energy charge in the development of milk goat mammary gland by high performance liquid chromatography. The results showed that adenylate pool was increased during pregnancy. Adenylate pool was sharp increased after the commencement of lactation and remains high leves during the whole lactation. In involution, adenylate pool were decreased.In these experiments, for the first time, the expression of glucose transporter-1(GLUT1) mRNA and GLUT1 was investigated in different period of dairy goat mammary gland by Real-time PCR and Western blotting .The localization of GLUT1 was detected in virgin, pregnancy, lactation and involution by confocal laser scanning microscope. These results showed that the expression of GLUT1 mRNA are similar to the expression of GLUT1 protein in different period of dairy goat mammary gland. The correlation is 0.83. In virgin, the expression of GLUT1 mRNA and GLUT1 was lowest and increased at the beginning of pregnancy. On 35 day of lactation, the expression of GLUT1 mRNA and GLUT1 reached the highest levels and remained high levels during the whole lactation. In involution, the expression of GLUT1 mRNA and GLUT1 was decresaed because apoptosis of mammary epithelial cells. In virgin and early pregnancy, GLUT1 was found in ductal epithelial cells; in late pregnancy and lactation, GLUT1 was detected in alveolus epithelial cells near to the basal lamina and extracellular matrix; in involution, mammary fat pad restored and GLUT1 was existed alveolus epithelial cells.In order to clarify the rule of energy metabolism regulation, (1) The expression of AKT mRNA, HKⅡmRNA and LDH mRNA was detected by Real-time PCR in different development period of dairy goat mammary gland. These results showed that AKT mRNA, HKⅡmRNA and LDH mRNA resched high levels during lactation. On 35 day of lactation, the expression of these genes reached the highest levels. The activation of AKT can increase total cellular ATP content by induced glycolysis and oxidative phosphorylation. High levels of AKT mRNA, HKⅡmRNA and LDH mRNA during lactation indicated that AKT may regulate mammary energy metablism during lactation. (2) The expression of LKB1 mRNA, AMPKα2 mRNA and AMPKβ1 mRNA was detected by Real-time PCR in different development period of dairy goat mammary gland. These results showed that LKB1 mRNA, AMPKα2 mRNA and AMPKβ1mRNA have high levels on one day and 35 day of lactation. The demand for energy was increased on one day and 35 day of lactation. These results indicated that AMPK may regulate mammary energy metablism.In order to clarify the effect of AMPK on the energy metabolism of mamary gland, mammary epithelial cells were cultured in a synthetic medium with 5-amino-4-imidazolecarboxamide-riboside (AICAR) in vitro. Mammary epithelial cells were cultured for 15min, 30min and 60min with AICAR. The results showed that AMPK can be activated significantly by AICAR (p<0.05). Compared with control group, the expression of GLUT1 mRNA was increased in activated group (p<0.05) and glycogen synthase-1 (GYS1) mRNA was decresed (p<0.05). Glucose uptake was increased in activated group (p<0.01); the expression of CPT1 mRNA was increased in activated group CPT1 (p<0.05) ; the expression of fatty acid synthase (FAS) mRNA and acetyl-coa carboxylase-1 (ACC) mRNA was decreased (p<0.05). Compared with control group, the expression of ribosomal protein S6 kinases (S6K1) mRNA was increased in activated group (p<0.05)and 4E-BP1 mRNA was no influence (p>0.05).
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