Nanoparticles (Al2O3, CuO, TiO2) Decrease ATPase Activity in the Osmoregulatory Organs of Freshwater Fish (Oreochromis niloticus); Histopathological Investigations of Tissues by Transmission Electron Microscope

Abstract

The use of nanoparticles (NPs) in diverse field of nanotechnology has been increased in the last decades and especially the aquatic environments have been contaminated by waste products. Because the potential toxic effects of NPs have been documented in different groups of animals, the present study was carried out to help understanding the toxic effects of three NPs in freshwater fish. In this work, Oreochromis niloticus were exposed to aluminum oxide (Al2O3), copper oxide (CuO) and titanium dioxide (TiO2) NPs in differing concentrations (0, 1, 5, 25 mg/L) for 14 d. Following the exposures, the activities of total ATPase, Mg-ATPase and Na, K-ATPase in the osmoregulatory organs (gill, kidney) of fish were measured. Additionally, the aggregates of NPs in the gill and intestine of fish which are the possible entrance to the blood stream were demonstrated by a transmission electron microscope (TEM) to demonstrate the histopathological effects of NPs. Thus, the aim of this study was to evaluate the relationship between the histological view of tissues and changes in ATPase activity. Data showed that all NPs decreased significantly (P 0.05) in ATPase activity in the gill. Overall, data demonstrated that the least affected enzyme was Mg-ATPase and the least toxic NP was Ti-NP. TEM images demonstrated that all NPs accumulated in the tissues of fish in 14 days of exposure period, but not eliminated completely after 14 days of depuration period. There were considerable changes in histological images between control fish tissues and NP exposed fish tissues. NP aggregates in the intercellular space and in the cells can be seen from the TEM images, indicating the decreases in ATPase activities occurred due to histopathological changes. This study demonstrated that NPs are able to cause changes in tissue structures and ATPases were very sensitive to NP exposures. Data suggested that there should be more studies to understand better the toxic effects of NPs in fish.