Oddy V H, Lindsay D B, Fleet I R
AFRC Institute of Animal Physiology, Babraham, Cambridge, UK.
J Dairy Res. 1988 May;55(2):143-54. doi: 10.1017/s0022029900025978.
Lactating goats were given a close arterial infusion of [1-14C]leucine and [4,5-3H]4-methyl-2-oxopentanoic acid into one half of the mammary gland at 2-3 weeks and 34-39 weeks after kidding. Rates of protein synthesis, degradation and net output were determined from measurements of arteriovenous difference and blood flow using a model of leucine metabolism previously developed for muscle (Oddy & Lindsay, 1986). Protein leucine output in milk (Y mumol/min) correlated well with the difference between synthesis and degradation (X mumol/min) derived from the model: Y = 1.30 + 1.24X (r2 = 0.9; n = 9, P less than 0.01). There was substantial synthesis and degradation of protein within the mammary gland. Although only an approximate value could be obtained for the partitioning of protein synthesis and degradation between tissue and milk proteins, there was evidence of appreciable turnover of both. There was no significant difference between mammary leucine and protein metabolism in early and late lactation other than that imparted by a greater mass of mammary tissue in early lactation, although there was a tendency for greater oxidation of leucine in late lactation.
在产羔后2 - 3周和34 - 39周时，给泌乳山羊的一侧乳腺进行[1 - 14C]亮氨酸和[4,5 - 3H]4 - 甲基 - 2 - 氧代戊酸的动脉内输注。使用先前为肌肉建立的亮氨酸代谢模型（Oddy和Lindsay，1986），通过测量动静脉差异和血流量来确定蛋白质合成、降解和净输出率。牛奶中蛋白质亮氨酸输出量（Y μmol/分钟）与模型得出的合成与降解之差（X μmol/分钟）相关性良好：Y = 1.30 + 1.24X（r2 = 0.9；n = 9，P < 0.01）。乳腺内存在大量蛋白质的合成和降解。尽管只能获得蛋白质合成与降解在组织蛋白和乳蛋白之间分配的近似值，但有证据表明两者都有明显的周转。除了早期泌乳时乳腺组织量更大所带来的影响外，早期和晚期泌乳时乳腺亮氨酸和蛋白质代谢没有显著差异；不过晚期泌乳时有亮氨酸氧化增加的趋势。
