Backwell F R, Bequette B J, Wilson D, Calder A G, Metcalf J A, Wray-Cahen D, MacRae J C, Beever D E, Lobley G E
Rowett Research Institute, Bucksburn, Aberdeen, United Kingdom.
Am J Physiol. 1994 Jul;267(1 Pt 2):R1-6. doi: 10.1152/ajpregu.1994.267.1.R1.
Specific use by the mammary gland in vivo of amino acids (AA) of peptide origin has been demonstrated in lactating dairy goats using a dual-labeled tracer technique involving close-arterial (external pudic artery, EPA) infusion of 13C-labeled dipeptides. The extent of utilization does not appear to differ for glycyl-L-[1-13C]phenylalanine and glycyl-L-[1-13C]leucine, perhaps indicative of a common mechanism by which AA are incorporated from peptide into milk protein. [1-13C]phenyl-alanine of peptide origin appears to be concentrated within the red blood cell, suggesting a role for the erythrocyte in peptide metabolism in vivo. In conclusion, it appears that the lactating mammary gland of goats has the ability to utilize AA of peptide origin for milk protein synthesis, and while the mechanism by which [1-13C]AA are incorporated into milk protein is not clear, it may involve peptide hydrolysis by either mammary cell surface or red blood cell hydrolases followed by uptake of liberated AA by the mammary gland.
在泌乳奶山羊中，使用双标记示踪技术（包括经阴部外动脉（EPA）近动脉输注13C标记的二肽）已证明乳腺在体内对肽源性氨基酸（AA）的特定利用情况。甘氨酰-L-[1-13C]苯丙氨酸和甘氨酰-L-[1-13C]亮氨酸的利用程度似乎没有差异，这可能表明AA从肽掺入乳蛋白存在一种共同机制。肽源性[1-13C]苯丙氨酸似乎集中在红细胞内，这表明红细胞在体内肽代谢中发挥作用。总之，山羊的泌乳乳腺似乎有能力利用肽源性AA进行乳蛋白合成，虽然[1-13C]AA掺入乳蛋白的机制尚不清楚，但可能涉及乳腺细胞表面或红细胞水解酶对肽的水解，随后乳腺摄取释放的AA。
