We have studied L-valine transport by the caecal segments of 6- to 8-week-old chickens. Isolated enterocytes from the proximal caecum incubated with 0.1 mM L-valine can accumulate the substrate against a concentration gradient. After 50 min incubation, the intracellular L-valine concentration reached 0.53 mM, a value higher than that observed in enterocytes from the jejunum (0.34 mM; P< 0.01). 2. Enterocytes from the medial and distal caccal regions are unable to transport L-valine uphill (cell concentration: 0.1 mM). 3. Amino acid accumulation by proximal caecal cells was Na+ -dependent and was inhibited by ouabain and 2,4-dinitrophenol. L-methionine inhibits L-valine uptake and a 2.5 mM concentration abolishes the capacity of enterocytes to accumulate the substrate. 4. The high accumulation ratios shown by the proximal caecum for L-valine suggest a role for this intestinal segment in the absorption of neutral amino acids present in the caecal chamber.
摘要
我们研究了6至8周龄鸡盲肠段对L-缬氨酸的转运。从近端盲肠分离出的肠细胞与0.1 mM L-缬氨酸一起孵育时，能够逆浓度梯度积累底物。孵育50分钟后，细胞内L-缬氨酸浓度达到0.53 mM，这一数值高于在空肠肠细胞中观察到的浓度（0.34 mM；P<0.01）。2. 来自盲肠中部和远端区域的肠细胞无法向上运输L-缬氨酸（细胞浓度：0.1 mM）。3. 近端盲肠细胞对氨基酸的积累依赖于Na+，并受到哇巴因和2,4-二硝基苯酚的抑制。L-甲硫氨酸抑制L-缬氨酸的摄取，2.5 mM的浓度会消除肠细胞积累底物的能力。4. 近端盲肠对L-缬氨酸显示出的高积累率表明该肠段在吸收盲肠腔内存在的中性氨基酸方面发挥作用。
