P-糖蛋白对布格呋喃大鼠肠道吸收的影响

本研究采用Caco-2细胞摄取和转运模型、大鼠小肠在体循环灌注、大鼠离体小肠翻转肠小囊模型及P-糖蛋白抑制剂维拉帕米(verapamil)和环孢素(cyclosporine A，CsA)研究P-糖蛋白(P-glycoprotein，P-gp)对布格呋喃(buagafuran)自肠道吸收的影响，UV-HPLC方法测定布格呋喃含量。实验结果表明，布格呋喃可被Caco-2细胞转运和摄取，维拉帕米和环孢素可使布格呋喃由Caco-2细胞绒毛面(apical，A)向基底面(basolateral，B)的转运较对照组增加1.4和1.35倍，基底面向绒毛面的转运则减少为对照组的71%和75%。维拉帕米和环孢素可使低浓度布格呋喃摄取量分别增加4.4和3.4倍。布格呋喃自大鼠小肠吸收较快，灌流90 min后残留量仅为10%。维拉帕米和环孢素可加快布格呋喃吸收，以灌流后30 min最为明显(分别提高12.4%和21.5%)。在大鼠小肠翻转肠小囊内液中布格呋喃浓度可在10 min内下降86%。维拉帕米和环孢素均可使小囊液和小囊匀浆中布格呋喃含量明显升高。以上结果提示，布格呋喃是P-糖蛋白的底物，P-糖蛋白可阻碍布格呋喃在小肠的吸收。肠道P-糖蛋白的外排作用可能是导致布格呋喃生物利用度低的重要原因之一。

Effect of P-glycoprotein on the absorption of buagafuran in rat intestinal lumen

To study the effect of P-glycoprotein (P-gp) on the absorption of buagafuran in ileum, the concentration of buagafuran in Caco-2 cells, rat averted intestinal sacs and recirculating perfusion were determined by UV-HPLC method. Verapamil and cyclospirin A (CsA) were used as P-gp inhibitors. The results showed that the transportation of buagafuran across Caco-2 monolayer showed vectorial manner. The permeation of buagafuran from apical (A) to basolateral (B) side was 11% and 24.8% from B to A side. Verapamil and CsA were found to increase the transport of buagafuran by 1.4 and 1.35 fold from A to B side and decrease by 71% and 75% from B to A side, respectively, compared with control. The uptake of buagafuran in Caco-2 cell was also enhanced by P-gp inhibitors, especially in low concentration of buagafuran. Ninety percent of buagafuran was absorbed after 90 min perfusion. Verapamil and CsA were found to improve the absorption of buagafuran at all time points, especially at 30 min (12.4% and 21.5%, respectively). During the incubation, only 14% of buagafuran left in rat averted intestinal sacs, while buagafuran levels were increased in both intestine homogenate and sacs by adding verapamil and CsA. The results indicated that buagafuran was one of the P-gp substrates based on the present study. The absorption of buagafuran can be blocked by P-gp, resulting in the enhancement of buagafuran metabolism in intestine. The poor bioavailability of buagafuran may be partially due to the effect of P-gp on its absorption and transportation in intestinal lumen.