Salinity and/or nanoparticles (Al₂O₃, TiO₂) affect metal accumulation and ATPase activity in freshwater fish...

The osmoregulation system of freshwater fish is sensitive to salinity increase in water. There is no satisfactory data to our knowledge on the accumulation of metal-oxide nanoparticles (NPs) in tissues of O. niloticus and their effects on ATPases (Na,K-ATPase, Mg-ATPase, Ca-ATPase) in differing salinities. Thus, this study investigated the effects of salinity (0 and 10 ppt) and Al₂O₃ and TiO₂ NPs (1 and 10 mg NPs/L) on the response of ATPases in acute (2 days) and chronic (20 days) durations. Data showed that nanoparticles accumulated in the tissues of fish, gill tissues having the highest levels of Al and Ti in both acute and chronic durations. Interestingly, the higher salinity significantly increased (P < 0.05) NP accumulations in the tissues in acute exposures, whereas it significantly decreased (P < 0.05) in chronic exposures. Salinity increase caused significant decreases (P < 0.05) in ATPase activities (up to 54 %) in control fish from both exposure protocols. Likewise, NP alone exposures (up to 80 %) and salt+NP (up to 83 %) exposures generally caused significant (P < 0.05) decreases in ATPase activities compared to their controls. Similarly, salt+NP exposures also decreased ATPase activities compared to NP exposures alone. The present data demonstrated that salinity and/or NP exposures decreased ATPase activities in the gill of freshwater fish, emphasizing the possible hazardous consequences of salt inputs and NP discharges into freshwater systems.