THE EFFECT OF ACUTE TEMPERATURE STRESS ON BIOCHEMICAL INDICES AND EXPRESSION OF LIVER HSP70 mRNA IN GIFT NILE TILAPIA JUVENILES(OREOCHROMIS NILOTICUS)

Acclimated at 26℃ for 3 weeks,GIFT tilapias(Oreochromis niloticus) were then treated at 16℃,21℃,26℃(control),31℃ and 35℃ respectively by means of acute temperature stress,and some biochemical indices in serum and liver and expression of HSP70 mRNA were examined over 0—24 h.The results showed that serum cortisol levels for all groups except control group increased significantly over 0—24h(P0.05).Glucose(GLU) level was higher significantly than that of other groups during the period of 24h when fish were transferred to low temperature(16℃)(P0.05).Changes in serum total protein(TP),glutamic-pyruvic transaminase(ALT),glutamic-oxaloacetic transaminase(AST),lysozyme and Alkaline phosphatase(AKP) were increased and then decreased over 0—24h.Serum triglyceride content increased significantly and cholesterol decreased when fish were transferred to 16℃(P0.05).Malondialdehyde(MDA) in liver increased significantly when fish were transferred to 16℃ and 35℃ over 0—24h,superoxide dismutase(SOD) and catalase(CAT) activities were increased at first and then gradually declined.After temperature stress,expression level of HSP70 mRNA increased significantly,and reached the highest value after 6h and decreased significantly after 24h.Therefore,temperature stress could improve non-specific immunity in serum,anti-oxidative capacity in liver and expression level of HSP70 mRNA.In practice,we should pay close attention to temperature changes in aquaculture production in order to reduce stress on the fish immune function of the temperature effect.