Abstract: As an immunopotentiator, polysaccharose can enhance the adaptation of animals to environmental stresses. The effects of polysaccharose on the antioxidant function of Misgurnus anguillicaudatus under ammonia stress are unclear. In this study, Misgurnus anguillicaudatus was exposed to water containing ammonia concentration of 0, 100, 200, and 300 mg·L^-1 for 40 days, respectively. The experiment was divided into test group and control group. Misgurnus anguillicaudatus in test group was fed with the diet containing lentinan with a concentration of1.0mg·g^-1, while that in control group was fed with the diet without lentinan. On 0, 5, 10, 15, 20, 25, 30, 35 and 40 d of the experiment, we measured the activities of superoxide dismutase (SOD), catalase (CAT), acid phosphatase (ACP) and alkaline phosphatase (ALP) in liver and muscle of Misgurnus anguillicaudatus, to investigate the effects of lentinan on the antioxidant function of Misgurnus anguillicaudatus under ammonia nitrogen stress. The results showed that the activities of SOD, CAT, ACP and ALP in liver and CAT in muscle of the 100 mg·L^-1 test group were significantly higher than those in control group (P<0.05). On the 30th day, the activities of SOD, CAT in muscle and liver of 100 mg·L^-1 test group reached the highest values, which were (26.0±2.3), (39.0±3.1), (37.0±3.8) and (45.0±3.6) U·g^-1 respectively. On the 35th day, the activities of ACP and ALP in muscle and ACP in liver in the 200 mg·L^-1 test group and the activity of ALP in liver in the 100 mg·L^-1 test group reached the highest values, with (23.0±2.1), (39.0±4.1), (33.0±2.4) and (46.0±1.8) U·g^-1 respectively. Theseresults indicate that lentinan can improve the antioxidant capacity of Misgurnus anguillicaudatus under ammonia stress.

Key words: lentinan, Misgurnus anguillicaudatus, ammonia nitrogen stress, antioxidation.