Gill Histopathologies Following Exposure to Nanosilver or Silver Nitrate

Fish gill is the site for many crucial physiological functions. It is among the first sites of xenobiotic exposure, and gill histopathological alterations may be detected soon after toxicant exposure. Silver (Ag) is one of the most toxic metals to aquatic organisms mainly due to its ability to disrupt ionic regulation. The goal of this study was to determine the effect of ionic and nanoscale Ag on fathead minnow gills by examining gill histology and Na⁺/K⁺-ATPase immunoreactivity. Fathead minnows were exposed to two measured concentrations of silver nitrate (AgNO₃: 1.3 or 3.7 μg/L as Ag⁺), citrate silver nanoparticles (citrate-AgNP: 15 or 39 μg/L), and polyvinylpyrrolidone-AgNP (PVP-AgNP) (AgNP: 11 or 50 μg/L). Circulatory disturbances were the most prevalent gill alterations detected and were significantly increased in all Ag treatment groups compared to control. AgNO₃ (1.3 μg/L) was the only treatment that significantly elevated the number of total mucous goblet cells present. In all other Ag treatments, the percent of degenerated goblet cells was significantly increased compared to control. When the sum of all histopathological abnormalities (weighted index) was calculated, all Ag groups displayed a significantly higher index, with citrate-AgNP having the highest toxicity (index of 10 ± 0.32 versus 2.4 ± 0.6 in controls). Gill Na⁺/K⁺-ATPase immunoreactivity was decreased by Ag. These results indicated that both AgNO₃ and AgNP created similar disruptions in gill structure and ionic regulation, possibly due to the ionic Ag portion of each treatment.

鱼类鳃是众多关键生理功能的执行场所，同时也是外源性物质（xenobiotic）暴露的首要靶器官之一；在接触有毒物质后，可快速检测到鳃组织的病理组织学改变。银（Silver, Ag）是对水生生物毒性最为显著的金属之一，其毒性主要源于能够破坏生物体的离子调节功能。本研究旨在通过观察鳃组织形态学及钠钾腺苷三磷酸酶（Na+/K+-ATPase）免疫反应性，探究离子态与纳米尺度银对黑头呆鱼（fathead minnow）鳃组织的影响。实验中，黑头呆鱼分别暴露于三种银制剂的两个实测浓度梯度组：硝酸银（silver nitrate, AgNO3，以Ag+计为1.3或3.7 μg/L）、柠檬酸银纳米颗粒（citrate silver nanoparticles, citrate-AgNP，15或39 μg/L）以及聚乙烯吡咯烷酮包被银纳米颗粒（polyvinylpyrrolidone-AgNP, PVP-AgNP，以AgNP计为11或50 μg/L）。循环功能紊乱是本次检测到的最常见鳃组织病理改变，且所有银制剂处理组的该类改变均显著高于对照组。仅1.3 μg/L浓度的硝酸银处理组，其鳃组织内总黏液杯状细胞数量显著升高。其余所有银制剂处理组的变性黏液杯状细胞占比，均显著高于对照组。当计算所有病理组织学异常的总和（加权评分指数）时，所有银制剂处理组的该指数均显著升高，其中柠檬酸银纳米颗粒组的毒性最高（处理组指数为10±0.32，对照组为2.4±0.6）。银制剂暴露可降低鳃组织内钠钾腺苷三磷酸酶（Na+/K+-ATPase）的免疫反应性。上述结果表明，硝酸银与银纳米颗粒均可对鳃组织结构及离子调节功能产生相似的破坏作用，这可能源于各处理组中均含有的离子态银组分。