Linn was established to evaluate the first-pass effects. After the oral gavage at a dosage of 40 mg·kg^-1 for , the of P-glycoprotein in the intestinal and liver tissues was associated with the concentration of enrofloxacin in the plasma. The results showed that P-glycoprotein fragments (127 bp) were successfully amplified in both the intestinal and liver tissues of by using specific primers. The concentrations of enrofloxacin were determined by HPLC. Enrofloxacin can be rapidly absorbed in the intestine and infiltrated into the plasma. The concentration versus time in the intestine, liver and plasma of were well described by a two-department open model with first-order absorption. The of P-glycoprotein of both intestinal and liver tissues in the first hour were higher than the control group (<0.05) while that of the intestine in the second hour was s<0.01). The of P-glycoprotein of liver tissues in the second hour were higher than the control group (<0.05). These results suggest that P-glycoprotein may be involved in the enrofloxacin metabolism process in , providing a novel model for the potential utility of gene expression and drug metabolism studies in aquatic animals.