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Survival strategies of Wuchang bream (Megalobrama amblycephala) juveniles for chronic ammonia exposure: Antioxidant defense and the synthesis of urea and glutamine.
Comparative Biochemistry and Physiology C: Toxicology & Pharmacology ( IF 3.9 ) Pub Date : 2020-01-14 , DOI: 10.1016/j.cbpc.2020.108707
Honghui Guo 1 , Wang Lin 1 , Xueyang Wu 1 , Lingkai Wang 1 , Dandan Zhang 1 , Li Li 2 , Dapeng Li 2 , Rong Tang 2 , Liping Yang 1 , Yuming Qiu 1
Affiliation  

This study aimed to explore how Wuchang bream (Megalobrama amblycephala) survive and defend against the toxicity of ambient total ammonia nitrogen (0, 5, 10, 20 and 30 mg/L TA-N) during 30-day exposure. As a result, hepatic malondialdehyde and protein carbonylation as well as histopathological alterations increased with increasing TA-N level, which suggested that chronic ammonia exposure caused oxidative stress and damage in the liver of fish. Meanwhile, the activities of hepatic total superoxide dismutase (T-SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glucose 6-phosphate dehydrogenase (G6PD) as well as the mRNA expression of Cu/Zn sod, cat, gpx and g6pd were elevated significantly along with significant reduction of glutathione (GSH) and nicotinamide adenine dinucleotide phosphate (NADPH) (P < 0.05). These results indicated that hepatic antioxidant responses were activated to alleviate oxidative damages induced by ammonia, in which lower-concentration ammonia only initiate SOD-CAT-GR-G6PDH defense and higher ammonia activated the SOD-CAT-GPx-GSH-GR-G6PDH antioxidant response. In addition, significant increases of serum urea and hepatic ammonia, urea, glutamine, arginase as well as glutamine synthetase were detected with the increase of TA-N (P < 0.05), while serum ammonia levels kept stable (P > 0.05). The present findings further revealed that ammonia could be detoxified directly into glutamine and urea in Wuchang bream to cope with ammonia exposure. In conclusion, under chronic ammonia exposure, enhanced hepatic antioxidant responses as well as increased urea and glutamine synthesis worked in combination to allow Megalobrama amblycephala to defend against environmental ammonia toxicity.

中文翻译:

武昌(Megalobrama amblycephala)幼虫长期暴露于氨的生存策略:抗氧化防御以及尿素和谷氨酰胺的合成。

这项研究旨在探讨武昌(Megalobrama amblycephala)如何在暴露30天期间生存并防御周围总氨氮(0、5、10、20和30 mg / L TA-N)的毒性。结果,肝丙二醛和蛋白质羰基化以及组织病理学改变随TA-N水平的升高而增加,这表明长期暴露于氨会引起鱼肝中的氧化应激和损害。同时,肝总超氧化物歧化酶(T-SOD),过氧化氢酶(CAT),谷胱甘肽过氧化物酶(GPx),谷胱甘肽还原酶(GR)和葡萄糖6-磷酸脱氢酶(G6PD)的活性以及Cu / Zn的mRNA表达草皮,猫,gpx和g6pd显着升高,同时谷胱甘肽(GSH)和烟酰胺腺嘌呤二核苷酸磷酸(NADPH)显着降低(P <0.05)。这些结果表明,肝抗氧化剂反应被激活以减轻氨引起的氧化损伤,其中较低浓度的氨仅引发SOD-CAT-GR-G6PDH防御,而较高的氨激活SOD-CAT-GPx-GSH-GR-G6PDH抗氧化剂响应。另外,随着TA-N的增加,血清尿素和肝氨,尿素,谷氨酰胺,精氨酸酶以及谷氨酰胺合成酶显着增加(P <0.05),而血清氨水平保持稳定(P> 0.05)。目前的发现进一步表明,可以将武昌中的氨直接解毒成谷氨酰胺和尿素,以应对氨的暴露。总之,在长期接触氨的情况下,
更新日期:2020-01-14
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