A carrier-mediated transport for folate in basolateral membrane vesicles of rat small intestine.
A carrier-mediated transport for folate in basolateral membrane vesicles of rat small intestine.
复制标题
大鼠小肠基底外侧膜囊泡中载体介导的叶酸转运。
DOI：
10.1042/bj2470141
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Redha,R
中科院分区：
文献类型：
--
作者：
Said,HM;Redha,R
叶酸从肠细胞出口的机制，即通过基底外膜的运输，尚不清楚。在本研究中，我们利用大鼠肠基底外膜囊，研究叶酸在大鼠肠基底外膜上的转运。这些囊泡对叶酸的吸收表明底物被运输到囊泡腔内，而不是与膜表面结合。叶酸运输速率在孵育前1分钟呈线性，但随后下降，在孵育5分钟后达到平衡。叶酸转运呈饱和状态(1)随浓度变化，表观Km为0.6 +/- 0.17 μ m， Vmax为饱和状态。1.01 +/- 0.11 pmol/30 s / mg蛋白质；(2)被结构类似物5-甲基四氢叶酸和甲氨蝶呤（Ki = 2和1.4微米）竞争性抑制；(4)电中性的;(5) Na +独立;(6)对阴离子交换抑制剂4,4 ' -二异硫氰酸二苯乙烯-2,2 ' -二磺酸（DIDS）的影响敏感。这些数据表明叶酸在大鼠肠基底膜中存在载体介导的转运系统，并表明该转运过程是电中性的、Na+不依赖的、对阴离子交换抑制作用敏感的。
The mechanism of exit of folate from the enterocyte, i.e. transport across the basolateral membrane, is not known. In this study we examined, using basolateral membrane vesicles, the transport of folic acid across the basolateral membrane of rat intestine. Uptake of folic acid by these vesicles represents transport of the substrate into the intravesicular compartment and not binding to the membrane surface. The rate of folic acid transport was linear for the first 1 min of incubation but decreased thereafter, reaching equilibrium after 5 min of incubation. The transport of folic acid was: (1) saturable as a function of concentration with an apparent Km of 0.6 +/- 0.17 microM and Vmax. of 1.01 +/- 0.11 pmol/30 s per mg of protein; (2) inhibited in a competitive manner by the structural analogues 5-methyltetrahydrofolate and methotrexate (Ki = 2 and 1.4 microM, respectively); (4) electroneutral; (5) Na+-independent; (6) sensitive to the effect of the anion exchange inhibitor 4,4′-di-isothiocyanatostilbene-2,2′-disulphonic acid (DIDS). These data indicate the existence of a carrier-mediated transport system for folic acid in rat intestinal basolateral membrane and demonstrate that the transport process is electroneutral, Na+-independent and sensitive to the effect of anion exchange inhibition.