Abstract: Oral drug delivery of Norfloxacin was performed on the starlet (Acipenser ruthenus Linnaeus) and the Amur sturgeon (Acipenser schrencki Brandt) for 5 days according to the concentration of 0, 20, 40, 60, 80 and 100 mg/kg, respectively. The enzyme activities of superoxide dismutase (SOD) in the blood plasma and liver tissues were measured after drug withdrawal for 2 days. This study was aimed at knowing well about the SOD change trend in both two sturgeons under the different concentration of drug delivery, and analyzing the best concentration of Norfloxacin and the liver injury during the sturgeon culture. The results showed that SOD enzyme existed in both two sturgeons with a different degree and the SOD activities were higher in the livers than in the blood plasma no matter whether the drug was delivered or not. The change of SOD activities performed the same regular trend in the two kinds of tissues under the different drug delivery concentration, which increased by inducing firstly but then fell down by inhibition lately with a maximum value under the 40 mg/kg concentration. In the blood plasma, the SOD activities hardly changed through the period of drug delivery, which were higher in the starlet than in the Amur sturgeon under 40 mg/kg and lower under other kinds of drug delivery concentrations. However, the SOD activities fluctuated sharply through drug delivery in the liver tissues. Additionally, the SOD activities were higher in the starlet than in the Amur sturgeon under 0, 40,100 mg/kg. Among of them, SOD activities in the starlet were the highest under 40 mg/kg and produced a sharp peak value. This study suggested that Norfloxacin had a better effective and could not lead to liver injury when delivered with 30 to 50 mg/kg concentration.

Key words: Norfloxacin; Amur sturgeon (Acipenser schrencki Brandt); starlet (Acipenser ruthenus Linnaeus); superoxide dismutase (SOD)