The in vitro kinetics of uptake, transport and efflux of 9-nitrocamptothecin in Caco-2 cell model

AimTo study the kinetics of uptake, transepithelial transport and efflux of 9-nitrocamptothecin (9-NC). MethodsA human intestinal epithelial cell model Caco-2 cell in vitro cultured had been applied to study the kinetics of uptake, transport and efflux kinetics of 9-NC at small intestine. The effects of time, pH, temperature and P-glycoprotein inhibitors on the uptake of 9-NC were investigated. The determination of 9-NC was performed by HPLC. ResultsThe uptake and absorption of 9-NC were passive diffusion as the dominating process. The uptake of 9-NC is positively correlated to uptake time, and negatively correlated to pH and temperature. The inhibitors, cyclosporine A and verapamil, significantly enhanced the uptake amount of 9-NC (P<0.05). P_app of Basolateral to Apical was much more than that of Apical to Basolateral (2.6-6.9 fold). The efflux of 9-NC was fitted to apparent two-order process. The m₀ ［(148.0±2.2) pmol·cm^-2］ and the efflux rate (41.1 pmol·cm²·min^-1) on Apical side were higher than the m₀ ［(121±7) pmol·cm^-2］ (P<0.05) and the efflux rate (29.2 pmol·cm²·min^-1) on Basolateral side (P<0.01). ConclusionThe uptake and absorption of 9-NC were passive diffusion as the dominating process. P-glycoprotein had strong efflux effects on the uptake and transepithelial transport of 9-NC.