Indican (indoxyl-β-D-glucoside) is present in several Chinese herbs e.g. Isatis indigotica, Polygonum tinctorium and Polygonum perfoliatum. The major metabolite of indican was indoxyl sulfate (IS), an uremic toxin which was a known substrate/inhibitor of organic anion transporter (OAT) 1, OAT 3 and multidrug resistance-associated protein (MRP) 4. Methotrexate (MTX), an important immunosuppressant with narrow therapeutic window, is a substrate of OAT 1, 2, 3, 4 and MRP 1, 2, 3, 4. We hypothesized that IS, the major metabolite of oral indican, might inhibit the renal excretion of MTX mediated by OAT 1, OAT 3 and MRP 4. Therefore, this study investigated the effect of oral indican on the pharmacokinetics of MTX. Rats were orally given MTX with and without indican (20.0 and 40.0 mg/kg) in a parallel design. The serum MTX concentration was determined by a fluorescence polarization immunoassay. For mechanism clarification, phenolsulfonphthalein (PSP, 5.0 mg/kg), a probe substrate of OAT 1, OAT 3, MRP 2 and MRP 4, was intravenously given to rats with and without a intravenous bolus of IS (10.0 mg/kg) to measure the effect of IS on the elimination of PSP. The results indicated that 20.0 and 40.0 mg/kg of oral indican significantly increased the area under concentration-time curve0-t (AUC0-t) of MTX by 231% and 259%, prolonged the mean residence time (MRT) by 223% and 204%, respectively. Furthermore, intravenous IS significantly increased the AUC0-t of PSP by 204% and decreased the Cl by 68%. In conclusion, oral indican increased the systemic exposure and MRT of MTX through inhibition on multiple anion transporters including OAT 1, OAT 3 and MRP 4 by the major metabolite IS.

中文翻译：

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转运蛋白介导的大鼠和甲氨蝶呤的相互作用

Indican（吲哚酚-β-D-葡萄糖苷）存在于几种中草药中，例如板蓝根、蓼蓼和蓼蓼。indican 的主要代谢物是硫酸吲哚酚 (IS)，它是一种尿毒症毒素，是有机阴离子转运蛋白 (OAT) 1、OAT 3 和多药耐药相关蛋白 (MRP) 4 的已知底物/抑制剂。具有窄治疗窗的重要免疫抑制剂，是 OAT 1, 2, 3, 4 和 MRP 1, 2, 3, 4 的底物。我们假设口服印度的主要代谢物 IS 可能抑制 MTX 介导的肾排泄OAT 1、OAT 3 和 MRP 4。因此，本研究调查了口服 indican 对 MTX 药代动力学的影响。在平行设计中，大鼠口服 MTX，含或不含指标（20.0 和 40.0 mg/kg）。通过荧光偏振免疫测定法测定血清 MTX 浓度。为了阐明机制，将 OAT 1、OAT 3、MRP 2 和 MRP 4 的探针底物酚磺酞 (PSP, 5.0 mg/kg) 静脉内给予大鼠，无论是否静脉推注 IS (10.0 mg/kg)测量 IS 对 PSP 消除的影响。结果表明，20.0 和 40.0 mg/kg 口服指标显着增加 MTX 的浓度-时间曲线下面积（AUC0-t）分别为 231% 和 259%，平均停留时间（MRT）延长 223% 和分别为 204%。此外，静脉内 IS 显着增加了 PSP 的 AUC0-t 204%，并降低了 68% 的 Cl。总之，口服指示剂通过抑制包括 OAT 1 在内的多种阴离子转运蛋白，增加了 MTX 的全身暴露和 MRT，