Effects of Waterborne ZnO Nanoparticles and $Zn^{2+}$ Ions on the Gills of Rainbow Trout (Oncorhynchus mykiss): Bioaccumulation, Histopathological and Ultrastructural Changes

Özet

The aim of this study was comparing the toxic effects of zinc oxide nanoparticles (ZnO NPs) versus zinc ions ($Zn^{2+}$) at ahigh non-lethal (500µg/L) and a low environmental relevant (0.05µg/L) concentrations on gills of rainbow trout(Oncorhynchus mykiss) following 14 days of waterborne exposure. Structural alterations, histopathological anomalies, andzinc bioaccumulation were investigated in the gills using field emission scanning electron microscopy (FESEM), hematoxylinand eosin staining (H&E), and graphite furnace atomic absorption spectrophotometry (GFAAS) respectively. Some damagessuch as shortening and fusion of secondary lamellae, surface epithelium hypertrophy, and hyperplasia of the primary lamellaewere observed in the gill tissue. Histopathological alterations of gills were minimum in bot h none exposed (control) fish andfish exposed to 0.05µg/L $Zn^{2+}$. The severity of gill damages were higher in fish exposed to 500µg/L ZnO NPs compared to500µg/L $Zn^{2+}$ and 0.05µg/L ZnO NPs. The Zn accumulation in the gills was concentration-dependent such thatbioaccumulation order was as 500µg/L Zn2+> 500µg/L ZnO NPs ≈ 0.05µg/L $Zn^{2+}$> 0.05µg/L ZnO NPs> control. In summary,the results of present study showed that although the accumulation capability of $Zn^{2+}$ was higher than ZnO NPs, but NPscause more structural damages to gills compare to ions.