TOXICITY OF ZINC OXIDE NANO-PARTICLES ON SOME ENZYMATIC PARAMETERS OF Heterobranchus longifilis AND AMELIORATIVE POTENTIAL OF ASCORBIC ACID

The rapid increase in the use of Nano-particles (NPs) of metal oxides in the production of consumer's products has greatly impacted the environment negatively. The study examined the effects of ZnO-NPs on the enzymes activities in selected tissues of Heterobranchus longifilis. Juvenile H. longifilis were exposed to sub-lethal concentrations (6, 8, 10, 12 mg/l) of ZnO-NPs for 60 days. The ZnO-NPs-exposed fish were subsequently subjected to depuration phase to evaluate recovery. Fish were later treated with graded levels of ascorbic acids (AA) diet (50, 250, 500, and 1000 mg/kg diet) for 30 days to ameliorate the ZnO-NPs toxicity. After each experimental stage, fish from the control, ZnO-NPs-exposed, depurated and ameliorated groups were sacrificed for enzyme assay from the blood, gill and liver.

There was significant increase (P < 0.05) in the activities of enzymes alanine aminotransferase (ALT); aspartate aminotransferase (AST); lactate dehydrogenase (LDH); acetyl cholinesterase (AChE); total protein and glucose (Figures 1, 2, 3, 4, 5, & 6) as the concentration and exposure period increased compared to the control. At depuration phase, there was a reduction in each of these parameters but none was comparable to the control. However, ZnO-NPs-exposed fish ameliorated with 500 mg/kg diet exhibited significant reduction (P < 0.05) in all the parameters (Figures 7, 8, 9, 10, 11 & 12) compared to the control. The results indicated that the release of ZnO-NPs into the aquatic environment is dangerous to fish and may also cause health risk in man through food chain, while 500 mg AA/kg diet is capable of ameliorating the toxic effects of ZnO-NPs on fish.