慢性氨暴露对中华鳖幼鳖血浆总氨氮、皮质酮浓度及组织氨代谢酶活性的影响

Effects of chronic ammonia exposure on plasma total ammonia-nitrogen,corticosterone and ammonia metabolism related enzyme activity of juvenile soft-shelled turtle Pelodiscus sinensis

本文观测了慢性氨暴露对中华鳖(Pelodiscussinensis)幼鳖血浆总氨氮、皮质酮浓度及与氨代谢有关的酶活性的影响。将中华鳖暴露在总氨氮(TAN)浓度为32.4、57.6、83.5mg/L(分别记为1、2、3组)的水环境中饲养42d,以自然晾晒脱氯自来水饲养组为对照(记为0组),pH值控制在7.80-7.85。检测氨暴露2、4、8、24、48h、42d后血浆TAN与8、24、48h、42d后皮质酮浓度,42d后肝、肌肉与脑中谷氨酰胺合成酶(Glutaminesynthetase,GS)、谷氨酸脱氢酶(Glutamatedehydrogenase,GDH)的活性以及特定生长率(Specificgrowthrate,SGR)的变化。结果表明:0、1组血浆TAN随时间没有明显变化,2、3组血浆TAN随时间呈现先增加后降低的趋势,分别在8h和48h达到峰值,42d时各组间血浆TAN没有显著差异。氨暴露显著影响暴露初期血浆皮质酮水平,暴露后24h,1、3组血浆皮质酮水平显著高于对照组;42d后除2组外其他组间无显著差异。4组之间肝、肌肉和脑中GS活性均没有显著差异,肝和肌肉GDH(氨化和去氨化方向)活性也没有显著差异。各暴露组脑GDH活性和对照组相比差异不明显,但各处理组间氨化和去氨化方向脑GDH酶活差异显著。42d饲养期间各处理组SGR没有显著差异。

The present study investigated the influence of chronic ammonia exposure on plasma total ammonia-nitrogen （TAN）, corticosterone concentration and activities of enzymes involved in ammonia metabolism of juvenile soft-shelled turtle Pelodiscus sinensis. The turtles were randomly divided into three groups （marked as groups 1, 2 and 3）, which were exposed to three ambient TAN concentrations, 32.4, 57.6, 83.5 mg/L TAN for 42 days, respectively. A control group （group 0） was also set up in which the animals were reared in tap water with no extrinsic NH4CI. pH was maintained at 7.80 - 7.85. We examined the plasma ammonia levels at 2, 4, 8, 24, 48 h and 42 d, corticosterone levels at 8 h, 24 h, 48 h and 42 d. At 42 d, we measured the activities of glutamine synthetase （GS） and glutamate dehydrogenase （GDH） in liver, muscle and brain. The results showed that plasma ammonia concentrations in groups 0 and 1 did not vary significantly throughout the experiment, while those in groups 2 and 3 increased to a peak value at 8 h and 48 h respectively. By the end of the experiment at 42 d, there were no clear differences among the plasma ammonia levels of the four groups. Ammonia exposure showed significant acute influences on plasma corticosterone levels. The corticosterone levels of groups 1 and 3 increased to peak values at 24 h after exposure, significantly higher than the control. At 42 d, the plasma corticosterone level became similar between the control and the treatment groups, except for a novel high value in group 2. There were no prominent differences in liver, muscle and brain GS activities. Liver and muscle GDH activities also showed no significant differences between the groups. Brain GDH activity showed no clear differences between the treatment groups and the control, however, varied clearly among the treatment groups in both animating and deanimating directions. Specific growth rates （SGR） did not differ among all groups during the 42 d rearing period .