Effect of silver nanoparticles on some hematological parameters, gill histology and Metallothionein gene expression of Pangasianodon hypophthalmus

The current development of nanotechnology and the increasing number of nanotechnology products, cause nanotechnology industry has become an important pillar in the global economy. Aquatic environments that are very vulnerable act as a location for deposition and accumulation of the nanoparticles. Among the wide range of nanoparticles, silver nanoparticles are widely used for antimicrobial properties. The aim of this study was to assess the possible effects of silver nanoparticles on some physiological characteristics of Rainbow catfish, Pangasianodon hypophthalmus. Eighty-five fish (12 ± 0.26 g, 10.7 ± 0.46 cm) were randomly allocated to 5 glass tank (100 L). The experiment consisted of five treatments including: 1 μg/L silver nanoparticles (1Ag-NPs), 1 μg/L silver nitrate (1AgNO3), 20 μg/L silver nanoparticles (20Ag-NPs), 20 μg/L silver nitrate (20AgNO3) and control for 10 days. Fish liver sampling was performed at days 1, 5 and 10 (end of experiment) for Metallothionein (MT) gene expression analysis. Gill tissues were fixed in 10% formalin for histopathological studies at last day of expousure. After 1 and 10 days of exposure, the blood sampling was done and common hematological parameters were evaluated. A 62 bp cDNA motif of Mt was sequenced for the first time in Rainbow catfish. Relative gene expression of MT in the liver was measured using Real-time PCR method with 18s as an internal control and was significantly higher in the 20Ag-NPs treatment compare with control in all sampling times (p<0.05). Hyperplasia, shortening and looping of secondary lamellae were the main gill histopathological sign of rainbow catfish exposed to water born AgNPs and AgNO₃. The mean red blood cell counts (RBC), hematocrite and hemoglobin was increased in 20AgNPs on first day (P<0.05); While there was no difference between treatments at last day of exposure (P>0.05). In both first and last days, there were no significant change in secondary hematological indices (P>0.05). Based on the results of this study the toxicological effects of AgNPs especially at high concentration was obvious on the catfish, so it is necessary to consider this side effects of AgNPs as an antimicrobial component in aquaculture industry.

Key words: silver nanoparticl, hematology parameter, gill, Metallothionein, Rainbow catfish, Pangasianodon hypophthalmus.