Forsberg N E, Baldwin R L, Smith N E
J Dairy Sci. 1985 Oct;68(10):2544-9. doi: 10.3168/jds.S0022-0302(85)81135-8.
Mammary gland tissues from three lactating Holstein cows were sampled and slices incubated with various concentrations of glucose and in combinations with other substrates in Krebs-Ringer bicarbonate-based media. Conversions of 1-and 2-carbon-14 glucose to carbon dioxide, lactose, glyceride-glycerol, citrate, and fatty acids were determined. Glucose utilization increased asymptotically with glucose availability. Carbon dioxide, lactose, and glyceride glycerol production accounted for nearly 90% of glucose recovered. Only trace quantities of glucose were recovered as fatty acids. Estimates of apparent affinities for glucose use were in a physiological concentration range of glucose. Oxidation of glucose was positively correlated with availability of acetate. Acetate availability increased the ratio of 1-carbon-14 glucose to 2-carbon-14 glucose oxidation and decreased glucose conversion to fatty acids. Glucose conversion to glyceride-glycerol was not affected by acetate availability. Primary uses of glucose are in lactose and glyceride glycerol synthesis and formation of reduced nicotinamide adenine dinucleotide phosphate for lipogenesis. Extensive use of glucose for these purposes may limit amounts available for fatty acid synthesis.
采集了三头泌乳期荷斯坦奶牛的乳腺组织样本，并将切片置于基于 Krebs-Ringer 碳酸氢盐的培养基中，与不同浓度的葡萄糖以及其他底物组合进行孵育。测定了 1-碳-14 葡萄糖和 2-碳-14 葡萄糖向二氧化碳、乳糖、甘油酯甘油、柠檬酸盐和脂肪酸的转化情况。葡萄糖的利用随着葡萄糖可利用量呈渐近增加。二氧化碳、乳糖和甘油酯甘油的生成量占回收葡萄糖的近 90%。仅回收了痕量的葡萄糖作为脂肪酸。葡萄糖利用的表观亲和力估计值处于葡萄糖的生理浓度范围内。葡萄糖的氧化与乙酸盐的可利用量呈正相关。乙酸盐的可利用量增加了 1-碳-14 葡萄糖与 2-碳-14 葡萄糖氧化的比例，并降低了葡萄糖向脂肪酸的转化。葡萄糖向甘油酯甘油的转化不受乙酸盐可利用量的影响。葡萄糖的主要用途在于乳糖和甘油酯甘油的合成以及为脂肪生成形成还原型烟酰胺腺嘌呤二核苷酸磷酸。大量葡萄糖用于这些目的可能会限制可用于脂肪酸合成的量。
