The Effect Of Acute Cold Stress And Recovery On The Serum Biochemical, Immune Indices And Hsp70Gene Expression In The Tissues Of Gift Strain Nile Tilapia(Oreochromis Niloticus)

Genetically Improved Farmed Tilapia (GIFT) is the tilapia with genetically improved traits. It is the achievement of genetic improved plan performed by WorldFish Centre and Norwegian related organization. The GIFT tilapia has the advantage of fast growth, genetic stability and so on. In a word, it’s a new and important cultured species.Low temperature is an important stressor. It resulted in the change of the serum lysozyme, complement activity and other related immune indices in gilthead and also induced the change of serum biochemical indices such as glucose, triglyceride in milkfish. Moreover, it also resulted in the change of alanine amiotransferase, aspartate transaminase activity in common carp and large yellow croaker. Additionally, it is reported that the cold stress increased the level of Heat Shock Protein70in Atlantic salmon.So far, there is no report about the effect of cold stress and recovery on serum biochemical parameters, hormones and HSP70of tilapia. The objective of the study is to study the effect of cold shock and recovery on the physiological function of GIFT tilapia, moreover, it will offer some theoretical information to the study of anti-cold stress mechanism.1The effect of acute cold stress on serum biochemical, immune indices and hormone in GIFT tilapiaThe fish were randomly divided into two groups. One is the control group (25±1℃), the other is the treatment group (9±1℃). Each group is divided into5parellel experiments. Several indices were determined, such as glucose, cholesterol, triglyceride, ALT, AST, completement3, completment4, lysozyme, cortisol, triiodothyronine and thyroxine at0h、2h、6h、12h after the cold stress.The results showed that compared with the control group (25±1℃), the level of Glu increased significantly (P<0.05) at6h after the cold stress, Chol increased significantly at6h and12h (P<0.05), TG increased at2h and6h after the cold stress (P<0.05), the content of ALT increased at2h and12h (P<0.05); the level of AST, cortisol, T3increased significantly (P<0.05) at2h,6h and12h after the cold stress in the treatment group (9±1℃), however, the level of C3, C4, LSZ decreased significantly (P<0.05) at2h,6h and12h after the cold stress in the treatment group (9±1℃). It is obvious that acute cold stress exerted influence on the physiological function of GIFT tilapia, moreover it weaken the immunity of GIFT tilapia.2The effect of recovery after acute cold stress on serum biochemical and immune indices in GIFT tilapiaThe150healthy fish from Freshwater Fishery Research Centre were acclimated for30days. The experimental animals were divided into the control group which was cultured at (25±1)℃, cold stress group which was cultured at (9±1)℃and the recovery group which was cultured at (25±1)℃. After2h cold stress, some fish were sampled, others were recovered at (25±1)℃and sampled at6h、24h after recovery.The results were as following. Compared with the control group, the level of TG, Chol increased at2h after cold stress (P<0.05). The content of ALT increased significantly (P<0.05) at2h, even at6h after recovery (P<0.05). The level of AST both increased during cold stress and recovery period (P<0.05). On the opposite, the level of C3、C4、LSZ decreased during both cold stress and recovery period (P<0.05). The level of cortisol increased significantly (P<0.05) after cold stress and during the recovery periold, the content of T3increased after cold stress (P<0.05), but there was no significance after6h recovery, the level of T4had no significance after stress and the recovery.3The effect of acute cold stress and recovery on HSP70mRNA in four tissues of GIFT tilapiaThe experimental animals were divided into the control group which was cultured at (25±1)℃, cold stress group which was cultured at (9±1)℃and the recovery group which was cultured at (25±1)℃. The initial temperature of control group and the experiment maintained at (25±1)℃. After2h cold stress, some fish in cold stress group were sampled, others were recovered and sampled at6h and24h. Liver、spleen、kidney、heart tissues were collected to detect gene expression of HSP70.The results were as following. Compared with the control group, the level of HSP70mRNA in liver increased after12h cold stress and still increased during the recovery period (P<0.05). In spleen, it increased at6h and12h after stress and6h after recovery (P<0.05). The level in kidney increased at6h and12h after cold stress and24h after recovery (P<0.05). In heart, it increased at12h after cold stress (P<0.05), but there was no significance during the recovery period. In a word, the cold stress has some influence on the normal physiological function of GIFT tilapia, such as immunity and so on. Meanwhile, it also induce the level of heat shock protein70mRNA to increase in different tissues; during the recovery period, some indices have reached the normal level, but the level of HSP70mRNA further increased, this maybe indirectly showed that HSP70plays some role in the recovery after acute cold stress.