Involvement of human organic anion transporting polypeptide OATP-B (SLC21A9) in pH-dependent transport across intestinal apical membrane
Involvement of human organic anion transporting polypeptide OATP-B (SLC21A9) in pH-dependent transport across intestinal apical membrane
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DOI：
10.1124/jpet.103.051300
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发表时间：
2003-08-01
影响因子：
3.5
通讯作者：
Tamai, I
中科院分区：
文献类型：
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作者：
Kobayashi, D;Nozawa, T;Tamai, I
一些有机阴离子通过载体介导的转运机制(S)从胃肠道吸收，可能包括质子偶联转运、阴离子交换转运等。然而，定位于人肠上皮细胞顶膜的有机阴离子转运体的分子特性尚不清楚。在本研究中，我们聚焦于人有机阴离子转运多肽OATP-B，并检测了其在小肠中的亚细胞定位和功能。免疫组织化学方法检测OATP-B的定位。检测了3-硫酸雌酮和3-羟基-3-甲基戊二酰辅酶A还原酶抑制剂普伐他汀在OATP-B转染人胚胎肾293细胞中的转运特性。OATP-B免疫组织化学染色定位于人肠上皮细胞顶膜。OATP-B在pH为5.5时对3-硫酸雌酮和[C-14]普伐他汀的摄取高于pH为7.4时。[H-3]雌酮-3-硫酸酯转运被普伐他汀、芳香族阴离子化合物和阴离子交换抑制剂4，4‘-二异硫氰基二苯乙烯-2，2’-二磺酸所抑制，但不被小阴离子化合物如乳酸和醋酸所抑制。普伐他汀对[H-3]雌酮-3-硫酸酯摄取的抑制作用呈浓度依赖性，IC50值为5.5 mM。结果表明，OATP-B介导阴离子化合物的吸收，其活性可能在小肠表面的酸性小气候pH时最佳。因此，OATP-B在人体肠上皮细胞顶膜对阴离子化合物的吸收中起作用，尽管不能断定普伐他汀的pH依赖吸收是由OATP-B单独决定的。
Some organic anions are absorbed from the gastrointestinal tract through carrier-mediated transport mechanism(s), which may include proton-coupled transport, anion exchange transport, and others. However, the molecular identity of the organic anion transporters localized at the apical membrane of human intestinal epithelial cells has not been clearly demonstrated. In the present study, we focused on human organic anion transporting polypeptide OATP-B and examined its subcellular localization and functionality in the small intestine. Localization of OATP-B was determined by immunohistochemical analysis. Transport properties of estrone-3-sulfate and the 3-hydroxy-3-methylglutaryl- CoA reductase inhibitor pravastatin by OATP-B-transfected human embryonic kidney 293 cells were measured. OATP-B was immunohistochemically localized at the apical membrane of intestinal epithelial cells in humans. Uptake of estrone-3-sulfate and [C-14] pravastatin by OATP-B at pH 5.5 was higher than that at pH 7.4. [H-3] Estrone-3-sulfate transport was decreased by pravastatin, aromatic anion compounds, and the anion exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, but not by small anionic compounds, such as lactic acid and acetic acid. The inhibitory effect of pravastatin on the uptake of [H-3] estrone-3-sulfate was concentration-dependent, and the IC50 value was 5.5 mM. The results suggested that OATP-B mediates absorption of anionic compounds and its activity may be optimum at the acidic surface microclimate pH of the small intestine. Accordingly, OATP-B plays a role in the absorption of anionic compounds across the apical membrane of human intestinal epithelial cells, although it cannot be decisively concluded that pH-dependent absorption of pravastatin is determined by OATP-B alone.