Effects of norfloxacin on gill and serum ECOD,APND,and GST ac-tivity in Fenneropenaeus chinensis

Chinese shrimp,Fenneropenaeus chinensis,were fed 0 mg/kg(control,CK),15 mg/kg(low dose,LD),30 mg/kg(mid dose,MD) and 60 mg/kg(high dose,HD) norfloxacin(NFLX) for 7 d.We then measured the change in gill and serum ethoxycoumarin-O-deethylase(ECOD),aminopyrine N-demethylase(APND),and glu-tathione-S-transferases(GST) activity at 2,4,6,8,10,12,24,or 48 h after the last oral administration.The shrimp[(5.8±0.4 g)] were held in 200 L plastic tanks(n=20 shrimp/tank) at salinity of 25.1±0.7,(22.0±1.0)°C and pH 8.1±0.6.At each time point we randomly selected eight shrimp from each replicate.The shrimp were immediately frozen in liquid nitrogen and stored at ?70℃ until analysis.Gill and serum GST activity was inhibited by NFLX.GST activity was 12.01 U/mL after 4 h in the gill of the MD group and was only 8.87% the level in the CK group.Serum GST activity was 3.99-fold higher in the CK group than in the LD group after 24 h(P0.05).APND and ECOD decreased initially then increased and activity was significantly lower in all treatment groups at all times relative to the controls.Higher concentrations of NFLX were associated with increased inhibition of APND and ECOD.