Effects of Flavobacterium psychrophilum extracellular products and lipopolysaccharide antigens on the antioxidant enzyme system activity of rainbow trout (Oncorhynchus mykiss) fry

The aim of this study was to investigate the response of different doses of lipopolysaccharide (LPS) and extracellular product (ECP) antigens (25, 50, 100, 250, and 500 µg) obtained from Flavobacterium psychrophilum to changes in oxidative stress parameters (catalase [CAT], superoxide dismutase [SOD], glutathione peroxidase [GPx], glucose 6-phosphate dehydrogenase [G6PD], glutathione reductase [GR], and malondialdehyde [MDA]) in juvenile rainbow trout. For this purpose, 6 different doses of F. psychrophilum (102–106) were applied to the fish, and the lethal dose 50 % (LD50) value was determined as 1.33·104. Changes in MDA levels and antioxidant enzymes were determined by applying 25 % of the LD50 value to fish for 14 days. Accordingly, while F. psychrophilum increased GR, G6PD, GPx, and SOD activity, it decreased MDA levels and CAT activity. Initially, 25, 50, 100, 250, and 500 µg doses of ECP and LPS were applied to the fish; after 21 days, a 25 % dose of LD50 was applied to these fish. Fourteen days later, the fish were taken, and the changes in MDA levels and antioxidant enzymes were examined. As a result, it was determined that while ECP and LPS application decreased GR, G6PD, GPx, and SOD activity, there was an increase in MDA levels and CAT activity.