The role of ascorbic acid and its derivatives in resistance to environmental and dietary toxicity of aquatic organisms
The impact of hyposalinity, shallow water, handling, temperature, and nitrite on ascorbic acid concentrations in various fish organs has been studied by a number of authors.3, 4, 5, 6, 7
The concentration of ascorbic acid in different organs in fish fluctuates over the year. Thomas et al.3 showed that the ascorbic acid concentration is maximal in liver during the summer when the temperature is high, and minimal during the winter. This may be due to a decreased dietary intake of the vitamin at low water temperature. The highest ascorbic acid concentration was detected in the brain. In contrast to the liver, the concentration in the brain declined during the summer. Thomas5 showed that increasing water temperature caused a decline in brain ascorbic acid content in juvenile mullet (Mugil cephalus L). A temperature-dependent generation of reactive O2 due to lipid peroxidation has been shown in freshwater catfish (Heteropneustes fossilis).6 Furthermore, hepatic superoxide dismutase (SOD) activity increased, and the ascorbic acid concentration in the liver was significantly reduced at increased water temperatures. There were also declines in major phospholipids, which might be due to reactive metabolites formed as a result of lipid peroxidation. Elevated temperatures also caused decreased concentrations of ascorbic acid in both gill and air sac tissue of freshwater catfish.7 The increased SOD activity and depletion of ascorbic acid in different tissues suggest that SOD and ascorbic acid act as effective oxyradical scavengers as a result of temperature stress.