Foulkes E C
Am J Physiol. 1987 Jun;252(6 Pt 2):F1042-7. doi: 10.1152/ajprenal.1987.252.6.F1042.
The present work explores the contributions of basolateral carrier systems in tubular reabsorption of organic solutes. Reabsorption of sugars and amino acids, as previously shown, can be represented by a three-compartment linear model that predicts that 1) if basolateral transport contributes to sugar reabsorption, alpha-methylglucoside reabsorption compared with that of glucose should be characterized by a longer transepithelial transit time (TET) and a correspondingly increased cellular transport pool (S), and 2) saturation of basolateral amino acid carriers, or presence of competing amino acids or other basolateral transport inhibitors, should prolong TET of a test amino acid, and increase S above the expected value. Both predictions were fully confirmed. Heavy metal intoxication not only inhibits transport of amino acids at the brush border, but also prolongs their TET and increases the size of S for a given reabsorbed load. Basolateral extrusion of amino acids is more sensitive to metals than is uptake across the brush border. Although basolateral carriers accelerate return of reabsorbed solute to blood, their contribution to reabsorption does not seem to be mandatory.
本研究探讨了基底外侧载体系统在肾小管对有机溶质重吸收中的作用。如先前所示，糖和氨基酸的重吸收可用三室线性模型表示，该模型预测：1）如果基底外侧转运有助于糖的重吸收，那么与葡萄糖相比，α-甲基葡萄糖苷的重吸收应以更长的跨上皮转运时间（TET）和相应增加的细胞转运池（S）为特征；2）基底外侧氨基酸载体的饱和，或竞争性氨基酸或其他基底外侧转运抑制剂的存在，应延长测试氨基酸的TET，并使S增加至预期值以上。这两个预测均得到了充分证实。重金属中毒不仅抑制了氨基酸在刷状缘的转运，还延长了它们的TET，并在给定的重吸收负荷下增加了S的大小。氨基酸的基底外侧外排比通过刷状缘的摄取对金属更敏感。尽管基底外侧载体加速了重吸收溶质返回血液，但它们对重吸收的作用似乎并非必不可少。
