Effect Of Environmental Stress On Free Radical Level And Antioxidant Enzymes Activities Of Chinese Sturgeon, Acipenser Sinensis

This dissertation studied the effects of food deprivation, crowding stress, and thermal stress on free radical level and antioxidant enzymes activities of Chinese sturgeon, Acipenser sinensis. Free radical levels and antioxidant enzyme activities of Chinese sturgeon under above three factors were assayed. The issue how Chinese sturgeon adapted its homeostasis of free radical to change of the environment was discussed. This result provided the scientific base of evaluating the health conditions and acclimatization of Chinese sturgeon.1. Effect of starvation on reactive oxygen species and antioxidant enzyme activities in Chinese sturgeon serumThe serum level of reactive oxygen species (ROS) and related antioxidant enzymes were measured in Chinese sturgeon under the conditions of food deprivation. The results showed that there were no significant differences between fasting group and control group in serum ROS concentrations, catalase (CAT) activities, and malondialdehyde (MDA) levels. Compared with the control, a significant increase of GSH in fasting group in the first experimental week was observed, after which GSH restored to the normal levels. Regarding superoxide dismutase (SOD) activity of fasting group, a significant diminution was found from the third week of food deprivation to the end of the experiment. Even though the sturgeon went back to the control diet, SOD activity in sturgeon of fasting group maintained the lower level in contrast with that of the control. The results suggested, starvation did not increase the lipid peroxidation significantly, and antioxidant defense mechanisms in Chinese sturgeon were under the homeostatic conditions. 2. Effect of crowding stress on reactive oxygen species and antioxidant enzyme activities in Chinese sturgeon serumExperimental fishes were stocked at three rearing densities, low stocking density (LSD), median stocking density (MSD) and high stocking density (HSD). After 5 days exposure, the related indexes of ROS and antioxidant enzymes were measured. The results showed that ROS was affected significantly by stocking density (P<0.01), and there was a significant positive relationship between ROS and stocking density (SD). While, MDA was not significantly affected by stocking density, and there was a significantly negative relationship between them. CAT and SOD activities were not...