[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.