Amino acid availability affects amino acid flux and protein metabolism in the porcine mammary gland
Amino acid availability affects amino acid flux and protein metabolism in the porcine mammary gland
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DOI：
10.1093/jn/132.6.1224
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发表时间：
2002-06-01
影响因子：
4.2
通讯作者：
Trottier, NL
中科院分区：
文献类型：
--
作者：
Guan, XF;Bequette, BJ;Trottier, NL
用动力学模型研究了饲料氨基酸(AA)限制、充足和过量条件下猪乳腺(MG)赖氨酸、蛋氨酸和缬氨酸的跨膜通量动力学。3头哺乳母猪(每个处理3头)分别饲喂三种日粮：赖氨酸缺乏[LD，4.9赖氨酸和9.9 Valine(g/kg日粮)]、充足(对照，9.7和10.2)和Valine过量(VE，9.8和13.4)。在哺乳期第18天，颈静脉注入2-N-15-赖氨酸、5-甲基-H-2(3)-甲氧基丙氨酸和1-C-13-缬氨酸20.5h，每隔2h和1h分别采集乳汁、动脉血和乳静脉血。与对照组相比，饲喂LD日粮的母猪产奶量和窝产仔数显著降低(P<；0.05)。乳蛋白合成(PS)、分解(PB)和净蛋白合成(PS)的模型估计值在饲喂LD日粮的母猪中降低(P<；0.05)。饲喂LID饲料的母猪对赖氨酸的净摄取量下降(P<；0.05)，这是由于赖氨酸的内向和向外运输减少的结果。饲喂LD日粮的母猪蛋氨酸向内转运趋于减少(P<；0.10)，导致蛋氨酸净摄取量下降。饲喂VE日粮的母猪，与对照组相比，PB降低(P<；0.05)，PS无变化。与对照组相比，饲喂VE日粮的母猪的Valine向外转运和赖氨酸净摄取量降低(P<；0.05)，但Valine的净摄取量没有变化。总而言之，动力学模型提供的PS估计值与牛奶蛋白产量和乳蛋白摄入量的经验测量值相似。猪MG对赖氨酸和蛋氨酸的转运与乳腺PS的调节密切相关。赖氨酸的利用率对缬氨酸的跨膜通量影响不大。
A kinetic model was used to examine transmembrane flux kinetics of lysine, methionine and valine across the porcine mammary gland (MG) under dietary amino acid (AA) limiting, adequate and excess conditions. Lactating sows (3 per treatment) were offered three diets: lysine-deficient [LD, 4.9 lysine and 9.9 valine (g/kg diet)], adequate (Control, 9.7 and 10.2) and valine-excess (VE, 9.8 and 13.4). On d 18 of lactation, 2-N-15-lysine, 5-methyl-H-2(3)-methlonine and 1-C-13-valine were infused into a jugular vein for 20.5 h. Milk and arterial and mammary venous blood samples were collected at 2- and 1-h intervals, respectively. Compared with Control, milk yield and litter growth rate decreased (P < 0.05) in sows fed the LD diet. Model estimates of mammary protein synthesis (PS), breakdown (PB) and net PS decreased (P < 0.05) in sows fed the LD diet. Net uptake of lysine decreased (P < 0.05) in sows fed the LID diet as a result of decreases in inward and outward transport of lysine. Inward transport of methionine tended to be reduced (P < 0.10) in sows fed the LD diet, resulting in a decrease in net methionine uptake. In sows fed the VE diet, PB was reduced (P < 0.05) and PS unchanged compared with Control. Outward transport of valine and net lysine uptake were reduced (P < 0.05), but net valine uptake was unchanged in sows fed the VE diet compared with Control. In conclusion, the kinetic model provided estimates of PS that were similar to empirical measurements of milk protein output and mammary protein accretion. Transport of lysine and methionine by the porcine MG is closely linked to regulation of mammary PS. Lysine availability has little effect on the transmembrane flux of valine.