摘要:
银鲫(Carassius auratus),杂食性鱼类,是我国淡水主养品种之一。在富营养化湖泊中,它能以有毒微囊藻为主要食物,导致微囊藻毒素(MCs)在其组织中大量累积。为研究MCs在肠道内累积和代谢特征及其对肠道的毒性影响,分别以50和200 μg MC-LReq·kg-1剂量的MCs粗提液(主要含MC-RR和MC-LR)对银鲫进行腹腔注射,并在注射后1、3、12、24、48和168 h后取样。MCs的含量用LC-MS和HPLC进行定性和定量测定,结果发现,高低两剂量组银鲫肠中MCs的含量均在注射后1 h达最大值(分别为2.8和181.4 ng·g-1 DW),然后随暴露时间的延长迅速下降。相对于毒素的累积,MCs诱导的银鲫肠组织损伤具滞后性,注射后48 h内,高低两剂量组肠道的病理变化呈时间-剂量依赖性的增长,病理特征表现为肠上皮细胞排列紊乱,甚至出现坏死、溶解和脱落,杯状细胞数目显著增多,微绒毛结构破坏并伴随淋巴细胞浸润。实验结果表明,单次染毒后MCs在鲫肠道中迅速累积后降解,并造成时间-剂量依赖性组织损伤,且低剂量组的损伤是可逆的。
Abstract:
Crucian carp (Carassius auratus L.), an omnivorous fish, is a dominant fresh-water species in China. This carp can ingest a significant portion of toxic cyanobacteria in eutrophic lakes, leading to microcystins (MCs) accumulation in its tissues. To study the dynamics and toxic effects of MCs in the gastrointestinal tract, an acute toxic experiment was conducted in crucian carp injected intraperitoneally (i. p.) with extracted MCs (containing MC-RR and MC-LR mainly) at the doses of 50 μg and 200 μg MC-LReq·kg-1 respectively, and samples were taken at 1, 3, 12, 24, 48 and 168 h after injection respectively. Quantitative and qualitative determinations of MCs in the intestinal tract were conducted by HPLC and LC-MS, respectively. The MCs concentrations in the intestinal tract reached the maxima (2.8 and 181.4 ng MC-RR·g-1 dry weight for the 50 and 200 μg MC-LReq·kg-1 dose groups respectively) at 1 h post-injection, followed by sharp declines afterwards, whereas the pathological changes of the intestinal tract in both dose groups progressively increased within 48 h, including disorganization, necrosis, lysis and even exfoliation of intestinal epithelial cells, an increase of the number of goblet cells, loss of the structure of intestinal microvilli and the presence of infiltrating lymphocytes. This study suggested that MCs were quickly accumulated in the intestinal tract of crucian carp after a single injection and then degraded progressively, which caused intestinal pathological damage in a time and dose dependent manner. Moreover, recovery was observed in the intestinal tract in the 50 μg MC-LReq·kg-1 dose group at 168 h post-injection.
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