Effects Of Glutamine On Hydrogen Peroxide-induced Oxidative Damage In Intestinal Epithelial Cells Of Jian Carp (Cyprinus Carpio Var. Jian)

The present study explored the effects of glutamine on hydrogen peroxide (H₂O₂)-induced oxidative stress in isolated carp enterocytes. Firstly, in order to select an optimal H₂O₂ concentration to induce oxidative stress in enterocytes, cultures were treated with different concentrations of H₂O₂ (0-100μM) for 16 hours. The results showed that an increase of H₂O₂ concentrations beyond 15μM and 45μM enhanced LDH release and MDA levels in a dose-dependent manner, respectively (P＜0.01) . And there were significant correlations between glutamine content, lactate dehydrogenase activity and malondialdehyde levels in the culture medium (r₁=+0.840, P＜0.01; r₂=+0.763, P＜0.01).Secondly, we then examined the cytoprotective effects of glutamine under conditions of oxidative stress. Cells were treated with glutamine (0-20 mmol/L) in the presence of H₂O₂ (100μM) for 16 hours. The control cells were kept in the glutamine-free MEM only. Results showed that glutamine completely blocked H₂O₂-stimulated release of lactate dehydrogenase (P＜0.01) . Furthermore glutamine reduced H₂O₂-induced increase in malondialdehyde levels and protein carbonyl content to levels seen in the control cultures, which means glutamine maintains cell membrane interity, preventing lipids and protein oxidation. Glutamine treatment completely prevented the decrease in alkaline phosphatase , sodium-potassium ATPase,γ- glutamyl transpeptidase induced by H₂O₂ (P＜0.01) , which means glutamine maintains cell function. In addition, glutamine treatment completely prevented the decrease in anti-superoxide anion activitity ,anti-hydroxy radical activitity and the increase in nitric oxide content by H₂O₂ (P＜0.01) , which means glutamine promoted cell antioxidant capacity by removing free radical. Glutamine treatment completely prevented the decrease in superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase activities as well as reduced glutathione concentration and the ratio between reduced and oxidized glutathione induced by H₂O₂ (P＜0.01) ,which means glutamine enhances cell antioxidant capacity.In conclusion, hydrogen peroxide induced oxidative damage in IEC in a does-dependent manner. Glutamine completely prevents against H₂O₂-induced cytotoxicity in fish cells, due to its antioxidant potential. Thus, glutamine could maintain the cell structure and function during the conditions of oxidative stress.