Silver nanoparticles cause osmoregulatory impairment and oxidative stress in Caspian kutum (Rutilus kutum, Kamensky 1901).

Silver nanoparticles (AgNPs) are increasingly used in several industrial and household products because of their antibacterial and antifungal properties. Hence, there is an inevitable risk that these chemicals may end up in aquatic biotopes and have adverse effects on the fauna. In order to assess potential health effects on aquatic organisms, this study evaluated the effects of waterborne AgNP exposure for 7 days on a set of critical stress parameters in juvenile Caspian kutum (Rutilus kutum), an economically important fish in the Caspian Sea. The applied level 11 μg/l of AgNP is high compared to reported water concentrations and corresponds to 40% of the 96 h LC50 value, initially determined to be 28 μg/l. Gill heat shock protein 70 (hsp70) mRNA expression, Na+/K+-ATPase activity and enzymatic activities of liver superoxide dismutase (SOD), glutathione peroxidase (Gpx), lactate dehyrogenase (LDH) and alkaline phosphatase (ALP), and whole-body cortisol and thyroid hormones (T3 and T4) were measured as endpoints. Gill hsp70 mRNA expression increased and gill Na+/K+-ATPase activity decreased in AgNP-exposed fish compared to controls. The specific activities of all liver enzymes decreased significantly compared to controls. Whole-body cortisol and thyroid hormones decreased compared to controls. In conclusion, the study demonstrates that AgNPs cause oxidative stress and gill osmoregulatory disruption in Caspian kutum juveniles.