Heat stress-induced alterations of antioxidants in the freshwater fish Channa punctata Bloch

The effect of elevated temperature on the antioxidants in the freshwater fish Channa punctata was investigated. Fish stressed with an elevated temperature of 12°C, range ± 1°C over the ambient temperature for 3 h showed a significant (P < 0.05-0.01) reduction in the levels of antioxidants: reduced glutathione (GSH) and non-protein thiols. Activity of glutathione reductase was also reduced in all the tissues (liver, kidney and gills) after 3 h of heat stress and 24 h recovery. Catalase (CAT) showed enhanced activity in liver in both the conditions while gills and kidney showed a decreased CAT activity. Glutathione S-transferase (GST) activity in kidney and liver decreased significantly (P < 0.05-0.01) after 3 h of heat stress. At 24 h GST activity showed a tendency to normalize in all the tissues along with a concomitant increase in the GSH level in the kidney. Total and protein thiols in heat stressed fish when matched with controls, showed significant (P < 0.05) reduction in the kidney only with a transient increase in liver and gills. Heat shock also induced lipid peroxidation in 3 h heat-treated and recovery groups when compared with controls. Elevated temperature therefore resulted in tissue specific and time-dependent alterations of antioxidants in the fish. It also induced lipid peroxidation in various tissues.