Determination of atpase responses in different sizes of fish (Oreochromis niloticus) to metals (Cu, Cr) in waters with different hardness

Freshwater fish Oreochromis niloticus with different sizes were individually exposed to different copper and chromium concentrations in water with different hardness in different exposure periods. At the end of exposure periods, Na+,K+-ATPase, Mg+2-ATPase and Total-ATPase activities in the gills and Ca+2-ATPase activity in the muscle were measured. Moreover, levels of total protein and metal accumulation in the tissues were determined and consequently responses of ATPases to metal exposures under different conditions were evaluated.There were changes in ATPase activities in relation to water hardness and fish size in both acute (48 hours, 20 µM metal) and longer (144 hours, 10 µM metal) exposure periods. Generally, control fish living in hard water showed higher ATPase activities comparing to soft water. Fish living in soft water were more sensitive to metals especially to copper exposures than fish living hard water. Profound effects were determined in smaller fish. It seemed that ATPases more affected in acute exposures when compared to longer exposure periods. Generally, total protein levels did not change in both the gill and muscle. Metal accumulation occurred in the tissues, though chromium levels were below detection limits in most cases. In general, tissue ion levels did not also change significantly