The biochemical effects of lambda-cyhalothrin and thiamethoxam in different tissues of Oreochromis niloticus

The effects of neonicotinoid insecticide thiamethoxam and pyrethroid insecticide lambda cyhalothrin were investigated individually and in mixture, in liver, brain and gonad tissues of Oreochromis niloticus for 7 and 15 days of exposures. Fish were left for depuration in pesticide-free water for 7 days. Acetylcholinesterase (AChE), ethoxyresorufin-O-deethlyase (EROD), superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) activities, total antioxidant capacity (TAC), total oxidant status (TOS), oxidative stress index (OSI), glutathione (GSH), malondialdehyde (MDA) and protein carbonyl (PCO), estradiol and testosterone levels in blood, condition factor, hepatosomatic index (HSI) and gonadosomatic index (GSI) were determined. AChE and CAT activities decreased while EROD and SOD activities increased. Glutathione S-transferase activity increased in gonad tissue while it decreased in other tissues. Oxidative stress index and TOS increased while TAK decreased. Lipid peroxidation and protein carbonylation increased while serum estradiol and testosterone levels decreased. Also, a decrease in HSI and GSI were observed. Results of this study, antioxidant enzymes increased against thiamethoxam and lambda cyhalothrin exposures, but antioxidant defense in O. niloticus was insufficient. Increased OXI showed that pesticides caused to start oxidative damage in liver, brain and gonad tissues. Also, decreased estradiol and testosterone level as well as GSI demonstrated that thiamethoxam and lambda cyhalothrin may be considered as potential endocrine disrupting chemicals. Also, depuration period for 7 days was not adequate to eliminate the toxic effects of pesticides.