RESPONSES OF SUPEROXIDE-DISMUTASE, GLUTATHIONE-PEROXIDASE AND REDUCEDGLUTATHIONE ANTIOXIDANT DEFENSES IN GILLS OF THE FRESH-WATER CATFISH (HETEROPNEUSTES-FOSSILIS) TO SHORT-TERM ELEVATED-TEMPERATURE

Superoxide anion radical (O-2(-)) has been hypothesized as one of the possible factors involved in the oxidative stress in aquatic animals. The antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1) cataly zes the conversion of O-2(-) to hydrogen peroxide (H2O2) whilst glutat hione peroxidase (GSH-Px; EC 1.11.1.9) metabolizes the H2O2 to H2O in part of the cell (cytosol and endoplasmic reticulum). Reduced glutathi one (GSH) is an important antioxidant which serves, in part, to set th e redox status in tissues. In the present study the patterns of SOD an d GSH-Px activities and GSH content were investigated, in an experimen tal model of elevated temperature, in gills of the fish Heteropneustes fossilis in order to investigate whether temperature elevation for 1- 4 h may alter the antioxidant system. After an elevated temperature ex posure from 25 (control) to 37 degrees C, the SOD activity increased w hile GSH-Px activity and GSH content decreased significantly (p < 0.05 ) at 32 and 37 degrees C at 1-4 h in comparison to control. Neverthele ss a transient increase in GSH-Px activity was observed at 1 and 2 h a t 32 degrees C. The results at 27 degrees C temperature were non-signi ficant (P < 0.05) in comparison to control. During the extended hours (1 to 4 h) of each elevated temperature, a general trend of increase i n SOD activity at 32 and 37 degrees C was observed. However, GSH-Px ac tivity and GSH content were not changed significantly for most of the extended period of elevated temperature. In conclusion, the elevated t emperature caused changes in SOD and GSH-Px activities and GSH (thiol) content in gills. (C) 1997 Published by Elsevier Science Ltd.