Effect of CYP3A and P-glycoprotein on the absorption of buagafuran in rat intestinal lumen

The rat single-pass intestinal perfusion model was applied to study the effect of CYP3A and P-glycoprotein on the absorption of buagafuran in lumen of rats.  Buagafuran concentrations in intestinal   perfusate and blood in vena mesenterica collected at different time points after perfusion were determined by GC-MS.  Permeability coefficient of buagafuran was calculated by the equation P_lumen = −(Q/2πrl)Ln(C_out/C_in) and P_blood = (ΔM_B/Δt)/(2πrl<C>).  The effects of troleandomycin (TAO, CYP3A inhibitor), cyclosporin A (CYP3A/p-glycoprotein inhibitor) on the absorption of buagafuran in lumen were observed.  After rat single- pass intestinal perfusion, the cumulative amount of buagafuran in mesenteric vein of rat was 73.4, 82.9, and 98.3 pmol·cm⁻² and were increased 3.9, 4.6, and 5.6 fold by addition of inhibitor of P-gp (LSN335984), CYP3A (TAO) or P-gp and CYP3A (CsA), respectively.  Moreover, the metabolized fraction of buagafuran was decreased by 12%, 11% and 21% with inhibitors.  The results suggested that the poor bioavailability of buagafuran was mostly due to the interplay of P-gp and CYP3A on the absorption, transport and metabolism of buagafuran in  intestine of rats.