Effects Of Acute Hypoxia Stress On Tissue Enzyme Activities And Related Gene Expression In Mandarin Fish(Siniperca Chuatsi)

Mandarin fish is an important breed in China,is loved by consumers.This study was conducted to investigate the effects of hypoxia stress on the antioxidant enzymes,respiration-related enzymes,non-specific immune enzyme activities,and the expression of hypoxia-related genes and inflammatory factors.This paper analyzes the physiological response process of hypoxia stress to the stress of mandarin fish from the aspects of enzyme activity and related gene expression,and provides basic materials for its healthy breeding.The study was based on the mandarin fish,and[DO(2.8 ± 0.2)mg/L]was set in the acute hypoxia stress group,and normoxic[DO(6.5±0.2)mg/L]was used as the control group.The liver,gill,and head kidney tissue samples of the experimental group and the control group were taken at 0 h,6 h,12 h,24 h,48 h,and 96 h of hypoxia stress,respectively.The main results are as follows:1 Effect of acute hypoxic stress on antioxidant enzyme activities in the liverUnder acute hypoxic stress conditions,liver superoxide dismutase(SOD)activity,catalase(CAT)activity,trace reduced glutathione(GSH)content,alanine aminotransferase(GPT)activity,and malondialdehyde(MDA)content increased first and then decreased.The SOD activity and GSH content of the experimental group were significantly higher than those of the control group at 6 h of hypoxia stress(P<0.05,the same below);the SOD activity was not significantly different from that of the control group after 24 h;the trend of GSH content decreased from 6 hours to 96 hours of stress,but still significantly higher than the control group;the activities of CAT and GPT continued to decrease from 12 h to 96 h of hypoxia stress,which was still significantly higher than the control group.MDA content increased significantly at 24 h after hypoxia stress,and was still significantly higher than the control group at 96 h.The results show that acute hypoxic stress has a significant effect on the antioxidant enzymes in the liver of mandarin fish.The antioxidant system is activated under hypoxic conditions to cope with the effects of hypoxic stress on the body,but the antioxidant function is inhibited with time.2 Effects of acute hypoxia stress on the expression of respiratory-related enzymes in the gill and hypoxia-related genes in the liver.The lactate dehydrogenase(LDH)activity in the gill tissue of the experimental group first increased and then decreased,which was significantly higher than that of the control group at 6 h and significantly lower than that of the control group at 24 h;The ultra-micro total ATPase(ATPase)activity showed a trend of decreasing first,then increasing and then decreasing.The stress from 6 h to 96 h was significantly lower than that of the control group.After hypoxia stress,the relative expression of HIF-1α gene was significantly increased in 48 h;the relative expression of EPO gene first increased and then decreased,and it was significantly increased after 12 h of hypoxia stress;the relative expression of HSP90a gene increased first and then increased.The decreasing trend was significantly up-regulated at 6 h and then down-regulated to 12 h,which was the same as that of the control group.At 48 h,it continued to increase and was significantly higher than the control group,followed by down-regulation.The results show that acute hypoxia puts the mandarin fish in a stress state and requires energy to maintain the body’s homeostasis.The body attempts to provide the body with energy by stimulating anaerobic respiratory enzymes for anaerobic metabolism,and at the same time the hypoxic response signal pathway is activated.3 Effect of acute hypoxia stress on the expression of non-specific immune enzymes in head kidney and inflammation-related genes in the liver.The content of lysozyme(LZM)in the test group was increased first and then decreased.It was significantly higher in the hypoxic environment at 6 h than in the control group and recovered at 48 h.The acid phosphatase(ACP)activity showed a decreasing trend under stress.24 h was significantly lower than the control group until 96 h;alkaline phosphatase(AKP)activity showed a trend of first increase,then decrease and then increase.The stress reached the highest value at 12 h but was not significantly higher than the control group.It was significantly lower than the control group at 24 h,and then increased to 96 h,which was close to that of the control group.The IL-1β gene showed a trend of first increase,then decrease,and then increase.After 6 hours of stress,the relative expression level was significantly higher than that of the control group,the relative expression level was down-regulated at 12 h,and the relative expression level was significantly increased at 24 h.;the relative expression of IL-8 gene first increased and then decreased,and the relative expression of hypoxia 6 h-24 h was significantly higher than that of the control group;The relative expression of IRF-1 gene first increased and then decreased.The relative expression of 6 hours after hypoxia exposure was significantly higher than that of the control group,and then it was lowered to 24 hours and then significantly lower than that of the control group.The results of this study indicate that acute hypoxic stress can activate the body’s non-specific immunity and at the same time inflammatory factor genes are induced.It is speculated that the continuous inflammatory response is the cause of impaired oxidative damage in the mandarin fish.In summary,hypoxia can cause oxidative stress,energy metabolism changes,and inflammatory reactions in fish.The experimental results suggest that the reduction of dissolved oxygen below 2.8 mg/L in the actual breeding process will have an adverse effect on the mandarin fish.In the actual breeding process,close attention should be paid to the changes of dissolved oxygen content in the breeding water body to reduce the adverse effects of low oxygen stress on the fish body.