Effect of waterborne benomyl on the hematological and antioxidant parameters of the Nile tilapia, Oreochromis niloticus

The present study was conducted to determine the 96 h-LC50 of benomyl to the Nile tilapia, Oreochromis niloticus and to investigate the biochemical or hematological indices of blood and the alterations in the antioxidant enzymes of this fish in response to sublethal concentrations of benomyl. Fish weighing 71.61 +/- 12.05 g were used in this study; they were subjected to fasting for 4 weeks before treatment. An aqueous solution of benomyl (0, 0.5, 1, 2, 4, 8, and 16 mg L-1) was administered for 96 h to determine the LC50. The 96 h-LC50 value of benomyl was 4.39 (3.23-5.60) mg L-1 in the present study. For 5 weeks, the aqueous solution of benomyl (0, 100, 200, and 400 mu g L-1) was administered to investigate its effect on the hematological parameters and antioxidant enzymes. The predominant hematological findings in fish exposed to benomyl were as follows: no significant change in the Hb (g dL(-1)) level, MCV (mu m(3)), MCH (pg) and MCHC (%) as compared to the control. Benomyl exposure led to greater increases in the GPT, GOT (Karmen-unit), LDH (Wroblewski unit), total cholesterol, Fe, and Ca (mg dL(-1)) values, whereas the levels of ALP (KA unit), total protein, triglyceride, albumin, and Mg (mg dL(-1)) did not increase. Benomyl increased the in vivo HSI (%), GST (nmol min(-1) mg protein(-1)). and SOD (U mg protein(-1)) values in the fish livers in the test group, unlike those in the control group for 5 weeks. At concentrations higher than 100 mu g L-1, benomyl affected the GST and SOD levels of Nile tilapia in a dose- and time-dependent manner. The present findings suggest that the in vivo hepatotoxicity associated with benomyl may, in part, result from the hematological index, and antioxidants may provide limited protection against benomyl toxicity. (C) 2008 Elsevier Inc. All rights reserved.