Effect of N,N-diethyl-3-methylbenzamide and 2-hydroxy-4-methoxybenzophenone in fish on xenobiotic metabolizing enzyme activities and antioxidant system

Benzophenone-3 (BP-3) is one of the UV-filters found in sunscreen agent. It is also used in cosmetics. N,N-Diethyl-m-toluamide (N,N-diethyl-3-methylbenzamide or DEET) is the main ingredient of insect repellents. BP-3 and DEET are lipophilic chemicals and can accumulate in living organisms. The aim of this study is to determine the effect of combination of BP-3 and DEET on CYP1A-associated 7-ethoxyresorufin O-deethylase activity (EROD), CYP2B-associated 7-penthoxyresorufin O-depenthylase activity (PROD), glutathione S-transferase (GST) and antioxidant enzyme activities, catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) in rainbow trout (Oncorhynchus mykiss). For this purpose, rainbow trout samples were treated with two different doses of BP-3 and DEET (100 µg/L and 500 µg/L). Fish samples were randomly divided into eight groups namely control, solvent control (DMSO), 100 µg/L BP-3, 100 µg/L DEET, 100 µg/L BP-3 + 100 µg/L DEET, 500 µg/L BP-3, 500 µg/L DEET and 500 µg/L BP-3 + 500 µg/L DEET. Fish were treated with indicated amount of chemicals individually or in combinations for 9 days. Microsomes and cytosols were prepared from liver tissues. EROD and PROD activities were measured in microsomes, catalase, GST, GR and GPx activities were measured in cytosols. EROD activities of 100 µg/L BP-3, 500 µg/L BP-3 and 500 µg/L BP-3 + 500 µg/L DEET treated groups were significantly different from the control and the solvent control (DMSO) groups. EROD activities of 100 µg/L BP-3 + 100 µg/L DEET group were significantly different from all groups. PROD activities of 500 μg/L BP-3 and 500 μg/L BP-3 + 500 μg/L DEET groups were less than all groups. GST activities of 100 μg/L BP-3 + 100 μg/L DEET group were significantly different from the control. CAT activities of 100 µg/L DEET group were significantly different from all groups. GR activities of 500 µg/L BP-3 group were significantly different from all groups. GPx activities were less in all BP-3 and DEET treatment groups than that of the control group. The effect of BP-3 and DEET on EROD activity were also shown with in vitro inhibition studies. Both of these chemicals inhibited EROD activities in rainbow trout liver microsomes. The results of this study indicate that BP-3 and DEET individually and/or in combinations modified CYP1A, CYP2B, GST and antioxidant enzyme activities in rainbow trout.