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.

鱼类鳃是诸多关键生理功能的承载场所，同时也是生物体最先接触外源性物质的部位之一，因此在接触毒物后可快速观测到鳃的组织病理学改变。银（Silver, Ag）是对水生生物毒性最强的金属之一，其毒性主要源于可干扰离子稳态调节。本研究旨在通过观察鳃组织学结构与钠钾-ATP酶（Na⁺/K⁺-ATPase）免疫反应性，探究离子态与纳米尺度银对黑头软口鲦鳃组织的影响。实验鱼被暴露于三种经浓度标定的银处理体系：硝酸银（AgNO₃：以Ag⁺计为1.3或3.7 μg/L）、柠檬酸包被银纳米颗粒（citrate-AgNP：15或39 μg/L）以及聚乙烯吡咯烷酮包被银纳米颗粒（PVP-AgNP：11或50 μg/L），每组设置两个浓度梯度。循环系统紊乱是本次观测到的最主要鳃组织病变，且所有银处理组的该病变发生率均显著高于对照组。仅1.3 μg/L硝酸银处理组可显著提升黏液杯状细胞的总数量；其余所有银处理组的变性黏液杯状细胞占比均显著高于对照组。当计算所有组织病理学异常的总和（加权指数）时，所有银处理组的加权指数均显著升高，其中柠檬酸包被银纳米颗粒组的毒性最强，其加权指数为10±0.32，对照组仅为2.4±0.6。鳃组织的钠钾-ATP酶免疫反应性可被银抑制。上述结果表明，硝酸银与银纳米颗粒均可对鳃组织结构与离子调节功能产生相似的干扰效应，这可能源于各处理组中均含有的离子态银组分。