Effect of zinc oxide nano-particles on activities of biochemical enzymes in the tissues of <i>Heterobranchus longifilis</i>

Abstract

The unregulated release of nano-particles into the environment induces toxicity in living organisms by interfering with normal cell processes. This study  investigated the toxicity effects of both lethal and sub-lethal concentrations of ZnO-NPs on biochemical enzymes in the tissues of African catfish,   Heterobranchus longifilis, by exposing to lethal concentrations (0.00, 60.00, 80.00, 100.00 and 120 mg/l) and sub-lethal concentrations (0.00, 6.00, 8.00,  10.00 and 12.00 mg/l) of ZnO-NPs for 96 h and 45 d in static renewal bioassays with continuous aeration respectively. After the exposure periods, blood  was collected through the caudal fin of the fish from control and exposure groups and sacrificed to remove the gills and liver for biochemical assay. The  results revealed a significant (P<0.05) increase in the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate  dehydrogenase (LDH), acetyl cholinesterase (AChE), and the levels of total protein and glucose also increased significantly (P<0.05) in the blood, gills and liver with increase in the concentrations and exposure periods compared to the control. The alterations in the biochemical enzymes of the fish indicated  that the release of ZnO-NPs into aquatic environment could be dangerous and may cause health risk in man through food chain.