Assessment of mutagenic, hematological and oxidative stress biomarkers in liver of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) in response to sublethal verapamil exposure.

The influx of pharmaceutical drugs and their metabolites have been reported to cause negative impact on aquatic biota. In this study, effects of long-term exposure of verapamil on mutagenic, hematological parameters and activities of the oxidative enzymes of Nile tilapia, Oreochromis niloticus were investigated for 60 days exposure at the concentrations of 0.29, 0.58 and 1.15 mg L(-1) in the fish liver. The exposure resulted in significantly high (p < 0.05) micronuclei induction of peripheral blood cells at the peak on day 30 at 1.15 mg L(-1). Compared with the control, there was significant increase (p < 0.05) in white blood cell counts and red blood cell distribution width (RDW), with a reduction in hemoglobin (Hb), red blood cell counts (RBCs), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) level as the concentration of the drug increased. The indices of oxidative stress biomarkers (lipid peroxidation and carbonyl protein) showed elevated level, depicting a positive correlation with both time and concentration. More so, the activity of energy-related parameter (Na(+ )-K(+)- ATPase) in the tissue was significantly inhibited (p < 0.05) at the end of 60 days exposure period. Further, the activity of catalase (CAT) was inhibited while reduced glutathione (GSH) level was decreased in the liver tissue. There was increase in the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) after 30 days at 0.29 mg L(-1). The study demonstrated that prolonged exposure to verapamil at sublethal concentration can result in mutagenic effects and oxidative dysfunctions in O. niloticus.