[Study on absorption mechanism of genistein self-microemulsifying system in rat intestines].

OBJECTIVE: To investigate the absorption mechanism of genistein self-microemulsifying system in rat intestines. METHOD: The concentrations of phenol red and genistein by in situ perfusion in rats were determined by UV and HPLC, respectively. The effects of drug concentrations, pH, various intestinal segments and P-glycoprotein (P-gp) inhibitor verapamil on the absorption had been studied. RESULT: The absorption rate constant (Ka) of genistein had no significant difference at concentrations of 0.05-0.5 mg x mL(-1) and pH of 5.4-7.8 in perfusion. It was Ka of jejunum > ileum > duodenum > colon. The absorption of genistein in jejunum had significant difference (P < 0.05) compared with other parts of intestines. Ka was increased obviously when verapamil was coper-fused with genistein (P < 0. 05). CONCLUSION: The absorption of genistein self-microemulsifying system is a first order process with passive diffusion mechanism related to P-gp efflux. It can be absorbed at all segments of rat intestine, and the jejunum is the best absorption segment, pH had no special effect on the absorption of genistein self-microemulsifying system in rat intestine.