Effects Of Glutathione On Growth Performance And Antioxidant Ability Of GIFT Oreochromis Niloticus

The study was conducted to investigate the effects of dietary glutathione on the growth performance, tissue biochemical indexes and activities of non-specific immune related enzymes, antioxidant ability and resistance to nitrite exposure of GIFT Oreochromis niloticus. The quantitative real-time polymerase chain reaction was applied to evaluate the effects of dietary GSH on the mRNA expression of GH, IGF-1, GST, SOD genes. The contents and results of the study are as follows:1. Effects of dietary glutathione on growth performance, tissue biochemical indexes and activities of non-specific immune related enzymes of GIFT Oreochromis niloticus.720fish with initial weight of (3.27±0.04) g were randomly allocated into6groups. The fish were respectively fed the diets added with0,80,160,240,320and400mg/kg GSH, named G0, G80, G160, G240, G320and G400. After49days’feeding, weight gain rate, specific growth rate, protein efficiency ration and RNA/DNA ratio of liver in G320were significantly higher than those in GO (P<0.05), and feed coefficient was significantly lowered (P<0.05). Feed intake and hepatosomatic index were higher in GSH added groups than in G0, showing no significant difference (P>0.05). Among all groups, no significant difference was found in condition factor (P>0.05). The whole-body crude protein and crude lipid contents were significantly affected by dietary GSH levels (P<0.05), while the ash and dry matter content showed no significant difference (P>0.05). There was no significant difference in serum cholesterol, triglyceride and glucose content (P>0.05), but serum UN content was significantly lower in G320compared with GO (P<0.05). The IGF-1level in G160-G400was significantly higher than in GO and G80. Dietary GSH increased GH and T3level in serum and liver, but no significant difference was observed (P>0.05). Serum lysozyme activities increased significantly in G240, G320and G400than in the others (P<0.05), and liver LZM activities were significantly higher in G320and G400(P<0.05). Dietary GSH increased serum alkaline phosphatase, phenoloxidase and liver AKP, acid phosphatase activities, but no significant difference was shown (P>0.05). Serum nitric oxide synthase activities in G320were significantly higher than in GO (P<0.05). The results suggested that dietary GSH could significantly improve the growth performance, raise whole-body crude protein and crude lipid content, increase serum and liver IGF-1level, activities of non-specific immune related enzymes in GIFT Oreochromis niloticus. The optimum level of dietary GSH was calculated to be335.13mg/kg on the basis of WGR.2. Effects of dietary glutathione on the antioxidant ability and resistance to nitrite exposure of GIFT Oreochromis niloticus. After the above mentioned alternative experiment was finished, the serum and liver samples were prepared and applied to measure the antioxidant enzymes activities, total antioxidant capacity as well as the content of malondialdehyde. Furthermore, the nitrite exposure experiment was conducted. It was found that glutathione S-transferase activities in serum of G320and liver of G160-G240were significantly higher than those of GO (P<0.05). GSH supplementation had a significant effect on glutathione reductase activities in serum of G160-G240and liver of G320(P<0.05). Superoxide dismutase activities in serum were higher in GSH added groups than those in G0, but no significant difference was observed (P>0.05). Liver SOD activities in G240increased significantly compared with GO (P<0.05). Catalase activities in serum of G320and liver of G240were significantly higher than those of GO (P<0.05). Dietary GSH increased serum and liver GSH content to some extent (P>0.05). Total antioxidant capacity activities in serum of G240～G400and liver of G240were significantly higher compared with GO (P<0.05). Anti-O2-in serum of G320was significantly higher than that in GO and G80(P<0.05). Malondialdehyde content in liver of G80-G320significantly decreased in comparison with G0. Accumulative mortality rate under nitrite exposure for96h in G320was significantly lower compared with GO (P<0.05). In conclusion, dietary GSH could improve the antioxidant ability and resistance to nitrite exposure.3. Effects of dietary glutathione on the mRNA expression of growth and antioxidant related genes in liver of GIFT Oreochromis niloticus. After the above mentioned alternative experiment was finished, the liver sample was prepared. The mRNA expression of GH, IGF-1, GST, SOD genes were determined using quantitative real-time polymerase chain reaction. The results showed that GH mRNA expression had no significant difference among all the groups (P>0.05). The mRNA expression of IGF-1gene in G320was significantly higher than that of GO and G400(P<0.05). There was a significant increase of GST mRNA expression in G240～G400(P<0.05). A positive correlation was found between the expression of SOD mRNA and the level of dietary GSH supplementation (P>0.05). In conclusion, dietary GSH could induce the mRNA expression of growth and antioxidant related genes in liver of GIFT Oreochromis niloticus.