急性氨氮胁迫及毒后恢复对团头鲂幼鱼鳃、肝和肾组织结构的影响

为进一步了解氨氮对团头鲂幼鱼的毒性毒理影响,以体质量为(14.27±0.01)g的团头鲂幼鱼为研究对象,研究了氨氮胁迫对其鳃、肝、肾组织结构的影响。实验首先进行96h的氨氮胁迫,得出96h LC50,在此基础上,设置对照组(0.472 mg/L)和实验组(25 mg/L)两个氨氮浓度处理组,进行0、6、12、24、48h的氨氮胁迫,取样后剩余团头鲂幼鱼移入曝气自来水进行96h的毒后恢复实验。结果表明：96h LC50为56.492 mg/L；三种组织观察表明,氨氮胁迫6h,鳃丝毛细血管扩张,上皮组织增生；肝细胞肿胀,细胞核肿大,肝细胞空泡化；肾小球萎缩,肾小囊腔膨大,肾小管管腔缩小；胁迫12h,泌氯细胞增生,呼吸上皮细胞出现部分脱落；肝细胞水样变性、血窦扩张、细胞轮廓模糊,形成点状病灶；肾小管上皮细胞肿大、水样变性、浊肿；胁迫24h,鳃小片融合、变短,呼吸上皮细胞大面积脱落；肝细胞水样变性、血窦扩张严重,形成局部病灶；肾组织淋巴细胞浸润严重,充血,肾小球坏死,肾小管坏死；胁迫48h,鳃小片卷曲,上皮细胞部分脱落；肝细胞部分溶解、血窦扩张,形成点状病灶；肾小管上皮细胞坏死,肾小球坏死；96h恢复后,泌氯细胞和上皮组织增生严重；肝组织大面积细胞核肿大,血窦扩张；肾组织淋巴细胞浸润严重,肾小管坏死,肾小球坏死。实验表明,不同的器官之间病症的损伤程度是不同的,肝组织的损伤最严重,然后依次是鳃和肾。随着胁迫时间延长,鳃、肝和肾组织受到的损害增加,同时鱼体也产生防御反应,但96h的恢复期不足以让团头鲂幼鱼在胁迫中完全恢复,而恢复能力最差的是肾组织。

Acute effects of ammonia exposure on histopathology of gill, liver and kidney in juvenile Megalobrama amblycephala and the post-exposure recovery

The aim of this paper is to investigate the toxic effects of ammonia-N stress on the histopathological changes of gill, liver and kidney of juvenile Megalobrama amblycephala.The M.amblycephala, whose initial average weight was(14.27±0.01)g, were first exposed to ammonia-N for 96 hours and then obtained the 96 hours median lethal concentration.Based on this, the juvenile M.amblycephala were exposed to two ammonia-N levels:0.472 mg/L(control group)and 25 mg/L(experimental group), each ammonia-N level was respectively sampled at 0, 6, 12, 24, 48 h, then the remainder of them were moved into aerated tap water for a 96 h post-exposure recovery.The results showed that the 96 h LC₅₀ of ammonia-N were found to be 56.492 mg/L.Fish exposed to different ammonia concentrations displayed histopathologic alteraions in the gills, liver and kidney.Gill tissues displayed hyperemia, epithelial hyperplasia, chloride cell hyperplasia, telangiectasis, epithelial necrosis and desquamation, epithelial and oedema, lamellar fusion curling of secondary lamellae as well as shortening of secondary lamellae.The liver showed hypertrophy of hepatocytes, cloudy degeneration, karyolysis, cellular peripheral nucleus, nuclear hypertrophy, hepato cellular vacuolation, dilatation in sinusoids, congestion, hydropic degeneration, necrosis, cellular outline indistinguishable and cytolysis;hypertrophied epithelial cells of renal tubules, reduction of space inside renal tubules, expansion of space inside, Bowman's capsule, contraction of the glomerulus, necrosis in tubular epithelium, cloudy swelling of epithelial cells of renal tubules, tubular necrosis, lymphocytic cell infiltration, renal tubules epithelial cells vacuolation, hydropic degeneration and hyperemia were observed in kidney.The results indicate that the severity of lesions clearly differed among organs with the liver showing the most extensive damages followed in order by the gills and kidney.The damages of gill, liver and kidney increase with increasing exposure time, in the meanwhile, the fish showed the self-regulation ability, however, it could not fully recover after a 96-hour post-expourse recovery and the kidney showed the worst recovery ability.