Fischer W J, Dietrich D R
Environmental Toxicology, University of Konstanz, Konstanz, Germany.
Toxicol Appl Pharmacol. 2000 Apr 1;164(1):73-81. doi: 10.1006/taap.1999.8861.
Mass occurrences of cyanobacteria, due to their inherent capacity for toxin production, specifically of microcystins (MC), have been associated with fish kills worldwide. The uptake of MC-LR and the sequence of pathological and associated biochemical changes was investigated in carp (Cyprinus carpio) in vivo over 72 h. Carp were gavaged with a single sublethal bolus dose of toxic Microcystis aeruginosa (PCC 7806) amounting to an equivalent of 400 microg MC-LR/kg body wt. Damage of renal proximal tubular cells and hepatocytes was observed as early as 1 h, followed by pathological changes in the intestinal mucosa at approximately 12 h postdosing. These alterations were characterized in hepatopancreas by a dissociation of hepatocytes, an early onset of apoptotic cell death, and delayed cell lysis. In the renal proximal tubules (P2) observations included increased vacuolation of individual tubular epithelial cells, apoptosis, cell shedding, and finally proteinaceous casts at the cortico-medullary junction. Concurrently with the pathological alterations, MC-immunopositive staining was observed in hepatocytes and the proximal tubular cells; the staining increasing in the hepatopancreas in intensity with increasing time postdosing. The presence of apoptotic cell death was determined using in situ fragment end labeling (ISEL) of the respective tissue sections and agarose gel electrophoresis for detection of DNA-laddering. The analysis of carp tissue extracts (hepatopancreas, kidney, GI tract, skeletal muscle, brain, heart, spleen, and gills) demonstrated MC-LR adducts having molecular weights of 38 kDa (putatively catalytic subunit of protein phosphatases-1 and -2A) and 28 kDa, respectively. An additional band was found to be present at 23 kDa in both hepatopancreas and kidney. The present data demonstrate that, in comparison to the pathological events in salmonids exposed to MC, where a slower development of pathology and primarily necrotic cell death prevails, the pathology in carp develops rapidly and at lower toxin concentrations. This is most likely due to a more efficient uptake of toxin, while the mechanism of cell death is primarily apoptosis.
蓝藻的大量繁殖，因其固有的毒素产生能力，特别是微囊藻毒素（MC）的产生能力，已在全球范围内与鱼类死亡事件相关联。在72小时内对鲤鱼（Cyprinus carpio）体内微囊藻毒素-LR（MC-LR）的摄取以及病理和相关生化变化的顺序进行了研究。给鲤鱼单次灌胃相当于400微克MC-LR/千克体重的亚致死剂量有毒铜绿微囊藻（PCC 7806）。早在1小时就观察到肾近端小管细胞和肝细胞受损，给药后约12小时肠道黏膜出现病理变化。这些改变在肝胰腺中的特征是肝细胞解离、凋亡性细胞死亡早期发生以及细胞溶解延迟。在肾近端小管（P2）中观察到的变化包括单个肾小管上皮细胞空泡化增加、凋亡、细胞脱落，最终在皮质-髓质交界处出现蛋白管型。与病理改变同时，在肝细胞和近端小管细胞中观察到MC免疫阳性染色；给药后随着时间的增加，肝胰腺中的染色强度增加。使用相应组织切片的原位片段末端标记（ISEL）和琼脂糖凝胶电泳检测DNA梯状条带，确定凋亡性细胞死亡的存在。对鲤鱼组织提取物（肝胰腺、肾脏、胃肠道、骨骼肌、脑、心脏、脾脏和鳃）的分析表明，MC-LR加合物的分子量分别为38 kDa（推测为蛋白磷酸酶-1和-2A的催化亚基）和28 kDa。在肝胰腺和肾脏中均发现另一条23 kDa的条带。目前的数据表明，与暴露于MC的鲑科鱼类中的病理事件相比，后者病理发展较慢且主要是坏死性细胞死亡，鲤鱼中的病理发展迅速且在较低毒素浓度下发生。这很可能是由于毒素摄取更有效，而细胞死亡机制主要是凋亡。
