DeSantiago S, Ramírez I, Tovar A R, Alonso L, Ortíz-Olaya N, Torres N
Departamento de Fisiología de la Nutrición, Instituto Nacional de la Nutrición Salvador Zubirán, México, D.F.
Rev Invest Clin. 1998 Sep-Oct;50(5):405-12.
To determine the free amino acid pool in plasma and milk in Mexican rural lactating women.
Twenty-eight women with an age 24 +/- 5.0 (+/- SD) years, weight 50 +/- 4.9 kg and height 148 +/- 4.8 cm were studied under metabolic balance conditions. Subjects were divided into five groups (three groups of lactation at 1st, 3rd and 6th month, one post-weaning group and a control group of non pregnant, non lactating women). Amino acid analyses of the diet and of plasma and milk samples were performed using an automated amino acid analyzer.
Differences were observed between the lactation groups and the other groups: aspartate increased at the 6th month (p < 0.05) while leucine, valine and isoleucine declined in the 3rd month (p < 0.05). In milk, valine, proline and taurine decreased at 6 months (p < 0.05), while serine and threonine raised at 3 months. Plasma levels were > 4 fold greater than milk levels for branched chain amino acids and for the basic, aromatic and neutral amino acids. In contrast, glutamate was 40 fold higher in milk than plasma and it was the predominant amino acid in the free pool of milk.
Our results suggest that the metabolic use of amino acids and the presence of specific amino acid transport systems during lactation, contribute to specific concentrations of free amino acids in milk that were not associated with the pool of free amino acids in plasma.
测定墨西哥农村哺乳期妇女血浆和乳汁中的游离氨基酸库。
对28名年龄为24±5.0（±标准差）岁、体重50±4.9千克、身高148±4.8厘米的妇女在代谢平衡条件下进行研究。研究对象分为五组（第1个月、第3个月和第6个月的三组哺乳期妇女、一组断奶后妇女以及一组非孕非哺乳期妇女作为对照组）。使用自动氨基酸分析仪对饮食、血浆和乳汁样本进行氨基酸分析。
观察到哺乳期组与其他组之间存在差异：第6个月时天冬氨酸增加（p<0.05），而第3个月时亮氨酸、缬氨酸和异亮氨酸下降（p<0.05）。在乳汁中，第6个月时缬氨酸、脯氨酸和牛磺酸减少（p<0.05），而第3个月时丝氨酸和苏氨酸增加。对于支链氨基酸以及碱性、芳香族和中性氨基酸，血浆水平比乳汁水平高4倍以上。相比之下，乳汁中的谷氨酸比血浆高40倍，并且是乳汁游离氨基酸库中的主要氨基酸。
我们的结果表明，哺乳期氨基酸的代谢利用以及特定氨基酸转运系统的存在，导致乳汁中游离氨基酸的特定浓度，这与血浆中的游离氨基酸库无关。
