Effect of elevated ammonia on tissue nitrogen metabolites in the ureotelic gulf toadfish (Opsanus beta) and the ammoniotelic midshipman (Porichthys notatus).
Effect of elevated ammonia on tissue nitrogen metabolites in the ureotelic gulf toadfish (Opsanus beta) and the ammoniotelic midshipman (Porichthys notatus).
复制标题
氨浓度升高对输尿管海湾蟾蜍 (Opsanus beta) 和氨输尿管候补生 (Porichthys notatus) 组织氮代谢的影响。
DOI：
10.1086/588829
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
McDonald,MD
中科院分区：
文献类型：
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作者：
Veauvy,CM;Walsh,PatrickJ;McDonald,MD
我们研究了解释海湾蟾蜍极端氨耐受性的可能生化途径，并专门测试了海湾蟾蜍Opsanus beta比两种同科物种平鳍鱼Porichthys notatus更耐受的预测，因为它逆转了高氨暴露期间脑内谷氨酰胺的积累。这一预测源于之前的研究，该研究表明海湾蟾蜍从谷氨酰胺中产生尿素，而氨水的见习官中不存在这种途径。我们的结果表明，在相同的水中 NH3 浓度下，见习官大脑中的氨比蟾蜍的大脑中的控制水平增加更多。在暴露于各自 LC50（96 小时）值 50% 的氨中 48 小时后，蟾蜍能够将氨引起的脑谷氨酰胺增加恢复到对照值，使脑谷氨酰胺减少 2,500 μmol kg−1。然而，在整个实验过程中，见习官的大脑谷氨酰胺仍显着高于对照组。蟾蜍暴露于33%的LC50（96小时）后，全身尿素最初增加，然后以104μmol·kg鱼−1h−1的速度减少，并可直接排泄到水中。我们讨论了蟾蜍中谷氨酰胺的特殊处理如何部分解释它们对氨的巨大耐受性。
We investigated possible biochemical pathways explaining extreme ammonia tolerance by the gulf toadfish and specifically tested the prediction that the gulf toadfishOpsanus betais more tolerant than the plainfin midshipmanPorichthys notatus, two confamilial species, because it reverses brain glutamine accumulation during high ammonia exposure. This prediction stems from previous studies demonstrating that gulf toadfish produce urea from glutamine, a pathway not present in the ammoniotelic midshipman. Our results show that at the same water NH3concentration, ammonia increases more from control levels in brains of midshipman than toadfish. After 48 h of exposure to 50% of their respective LC50(96 h) value for ammonia, toadfish are able to return the ammonia‐induced increase in brain glutamine back to control values, reducing brain glutamine by 2,500 μmol kg−1. However, in midshipman, brain glutamine remains significantly elevated from control throughout the experiment. Toadfish exposed to 33% of their LC50(96 h) showed an initial increase in whole body urea, which is then reduced at a rate of 104 μmol kg fish−1h−1and could be directly excreted into the water. We discuss how the special handling of glutamine in toadfish may explain in part their great tolerance to ammonia.