Cheeseman C I
Am J Physiol. 1986 Nov;251(5 Pt 1):G636-41. doi: 10.1152/ajpgi.1986.251.5.G636.
Quantitative autoradiography was used to measure the distribution of transport of leucine, lysine, and glycyl-L-leucine along the villus of the rat jejunum. A comparison was made between normal juvenile animals and ones maintained on a 5% protein isocalorific diet. Uptake of leucine, lysine, and glycyl-L-leucine was confined to the top 150 microns of the villus in control animals and initial expression of transport corresponded to a cell age of 32 h. The low-protein diet altered the distribution of transport in the same way for all three substrates, but although the position up the villus of the initial expression of transport was altered, transport always appeared in cells 32 h old. These data indicate that the age of intestinal epithelial cells is an important determinant of their ability to transport amino nitrogen. Transport kinetic data indicated that peptide uptake was initially elevated in response to the low-protein diet while free amino transport was depressed. It is concluded that a second locus of control determines the amount of transport expressed per individual cell.
采用定量放射自显影法来测定亮氨酸、赖氨酸和甘氨酰 - L - 亮氨酸沿大鼠空肠绒毛的转运分布情况。对正常幼年动物和食用5%蛋白质等热量饮食的动物进行了比较。在对照动物中，亮氨酸、赖氨酸和甘氨酰 - L - 亮氨酸的摄取局限于绒毛顶部150微米处，转运的初始表达对应于32小时龄的细胞。低蛋白饮食对所有三种底物的转运分布产生了相同方式的改变，尽管转运初始表达在绒毛上的位置发生了变化，但转运总是出现在32小时龄的细胞中。这些数据表明，肠上皮细胞的年龄是其转运氨基氮能力的一个重要决定因素。转运动力学数据表明，响应低蛋白饮食，肽摄取最初升高，而游离氨基酸转运则受到抑制。得出的结论是，第二个控制位点决定了每个细胞表达的转运量。
