Abstract
In sustainable aquaculture systems, copper sulfate (CuSO4) is widely applied as a disinfectant to control parasitic infections and algal growth. However, aquatic organisms may suffer from exposure to excessive concentrations of Cu. Elevated Cu concentrations could activate damage to the respiratory functions of aquatic animals. Thus, this study explored the effects exerted by ferulic acid (FA) on respiratory metabolism, oxidation-related lesions, and the apoptosis parameters of the gills and red blood cells in copper sulfate pentahydrate (CuSO4·5H2O)-treated carp (Cyprinus carpio var. Jian). When the 30-day feeding experiment was completed, the carp were exposed to 12.5 μM of Cu for 4 days. The results indicated that the Cu decreased the oxygen consumption and ammonia excretion rates in the carp, reduced the metabolic- and antioxidant-related enzyme activities and glutathione levels in the carp, and enhanced the caspase activities and reactive oxygen species and malondialdehyde levels in the gills of the carp. Moreover, in addition to the changes in the above parameters, the Cu decreased the cell numbers and hemoglobin concentrations and increased the phosphatidylserine exposure and cytochrome c levels in the red blood cells of the carp. These results demonstrate that Cu is capable of decreasing respiratory metabolism and increasing oxidation-related lesions and apoptosis inside the gills and red blood cells of the fish. However, dietary FA quenched the Cu-induced apoptosis and oxidative lesions by reversing the same biomarker indicators, thereby suppressing the Cu-induced decrease in respiratory metabolism. Thus, FA can be used as a suppressor of Cu stress in fish.