Dependence of intestinal amino acid uptake on dietary protein or amino acid levels.
Dependence of intestinal amino acid uptake on dietary protein or amino acid levels.
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DOI：
10.1152/ajpgi.1987.252.5.g614
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发表时间：
1987-05
期刊：
影响因子：
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通讯作者：
W. Karasov;D. Solberg;J. Diamond
中科院分区：
文献类型：
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作者：
W. Karasov;D. Solberg;J. Diamond
为了了解肠道氨基酸(AA)运输如何受到饮食底物水平的调节，我们测量了三种氮含量不同的等卡日粮中的一种的小鼠空肠刷状缘膜对七种氨基酸和葡萄糖的摄取。在高蛋白日粮中，非必需、毒性较小的氨基酸、脯氨酸和天冬氨酸的摄取量增加了77-81%，而毒性较高的必需氨基酸的摄取量仅增加了32-61%。在缺氮日粮中，非必需天冬氨酸和脯氨酸的摄取量下降，但必需氨基酸和非必需丙氨酸的摄取量保持不变或增加。这些模式意味着对肠道的各种AA转运蛋白的独立调节。随着饲料中氨基酸(或蛋白质)的减少，亚氨基酸和酸性氨基酸的“私人”转运蛋白受到抑制，而碱性氨基酸转运蛋白和中性的AA“公共”转运蛋白的活性下降到一个渐近线或经历一个最小值。这些调控模式可以理解为蛋白质作为卡路里、氮和必需氨基酸来源的多重角色和高浓度必需氨基酸的毒性之间相互冲突的限制之间的妥协。
To understand how intestinal amino acid (AA) transport is regulated by dietary substrate levels, we measured uptake of seven AAs and glucose across the jejunal brush-border membrane of mice kept on one of three isocaloric rations differing in nitrogen content. In the high-protein ration, uptake increased by 77-81% for the nonessential, less toxic AAs, proline, and aspartate but only by 32-61% for the more toxic essential AAs tested. In the nitrogen-deficient ration, uptake decreased for the nonessential aspartate and proline but stayed constant or increased for essential AAs and for the nonessential alanine. These patterns imply independent regulation of the intestine's various AA transporters. With decreasing dietary AA (or protein), the imino acid and acidic AA "private" transporters are repressed, while activities of the basic AA transporter and the neutral AA "public" transporter decrease to an asymptote or else go through a minimum. These regulatory patterns can be understood as a compromise among conflicting constraints imposed by protein's multiple roles as a source of calories, nitrogen, and essential AAs and by the toxicity of essential AAs at high concentrations.