Effects of copper, zinc, cadmium, chromium and silver on the Na+/K+-ATPase, Ca2+-ATPase and Mg2+-ATPase in gill, kidney and Ca2+-ATPase enzyme activities in muscle tissues of Oreochromis niloticus

Freshwater fish Oreochromis niloticus were individually exposed to different concentrations (0, 0.1, 0.5, 1.0, 1.5 µg/mL) of Cu2+, Cd2+, Cr6+, Ag+ and Zn2+ for 96 hours and 0.05 µg/mL concentration of same metals for different period of time (0, 5, 10, 20, 30 days). Following each period, Na+/K+-ATPase, Mg2+-ATPase, Total-ATPase, Ca2+-ATPase activities, total protein, metal and ion levels were measured in gill, kidney and muscle.Except Ag+, none of the metals killed fish within 30 days. Silver killed all fish within 16 days. While metal exposures generally decreased tissue Na+/K+-ATPase and Ca2+-ATPase activities, they increased Total-ATPase and Mg2+-ATPase activities beside their decreases after in vivo/in vitro acute and chronic durations. Metals accumulated in the tissues except Ag+ and Cr6+ due to their low levels below the detection limits and total protein levels enhanced or declined depending upon the tissue, metal, concentration and exposure duration. Na+ and K+ levels generally decreased, whereas Mg2+ and Ca2+ levels increased. Na+ was the most affected ion and Mg2+ was the least affected ion after metal exposure.