Verapamil caused biochemical alteration, DNA damage, and expression of hepatic stress-related gene biomarkers in Nile tilapia, Oreochromis niloticus

Sublethal diclofenac induced oxidative stress, neurotoxicity, molecular responses and alters energy metabolism proteins in Nile tilapia, Oreochromis niloticus

Reports have shown that residues of pharmaceuticals and their metabolites can pose toxicological threats to organisms living in aquatic ecosystem. Nile tilapia, Oreochromis niloticus, was exposed at 0.17, 0.34, and 0.68 mg L^-1 of diclofenac up to 60 days in a renewal static bioassay system. Antioxidant enzymes reactions, molecular responses, activities of energy metabolism proteins, and the neurotoxic potentials of the drug in the brain and fish muscle were evaluated. Antioxidant enzyme activities such as superoxide dismutase, glutathione-S-transferase, and also fructose 1, 6 bisphosphatase and glucose-6-phosphate dehydrogenase as well as the levels of lipid peroxidation and protein carbonyl were elevated, while glutathione peroxidase, total reduced glutathione, and acetylcholinesterase in the brain and muscles of the treated groups were significantly inhibited in a dose-dependent association. Expression of superoxide dismutase (sod), catalase (cat), and heat shock proteins (hsp 70) genes in brain and muscle tissues was up-regulated. Continuous treatment with sublethal diclofenac for a long time can induce oxidative imbalance, cause neurotoxicity, and alter the expression of genes related to stress in Nile tilapia, suggesting the use of these biomarkers in monitoring the adverse effects the pharmaceuticals could cause to organisms in aquatic ecosystem for possible mitigation.

Toxicity and genotoxic evaluations in African catfish Clarias gariepinus (Burchell 1822) exposed to Act Force Gold®, Butaforce®, and Atraforce®

Act Force Gold^®, Butaforce^®, and Atraforce^® are among the most commonly used pesticides in Nigeria. The lethal concentrations and the respective toxic units for the three pesticides were determined. The genotoxic effects of the three pesticides were investigated in the red blood cells of Clarias gariepinus using micronucleus (MN) assay. The 96 h LC₅₀ was 4.75, 4.84, and 54.74 mg L^-1 for Act Force Gold^®, Butaforce^®, and Atraforce^®, respectively. The toxic units in ascending order of toxicity were 1.83, 20.66, and 21.05 for Act Force Gold^®, Butaforce^®, and Atraforce^® respectively. The estimated safe levels based on NAS/NAE varied from 4.75 × 10^-1-4.75 × 10^-5 in Act Force Gold^® through 4.64 × 10^-1-4.85 × 10^-5 in Butaforce^® to 5.74-5.74 × 10^-5 in Atraforce^®. Fish specimens were exposed to the pesticides and sampling was done at regular intervals at days 1, 7, 14, and 21 and after another 7-day recovery period. The results obtained indicated concentration- and duration-dependent increase in % MN formation with maximum values of 3.40 ± 0.25 for Act Force Gold^® on day 14 and 3.05 ± 0.36 and 2.35 ± 0.14 for Butaforce^® and Atraforce^® respectively on day 7 of exposure. The 7-day recovery period could not reverse the trend as the % MN values obtained were significantly different from the control. The results further support the use of MN assay in assessing the toxicity of aquatic pollutants and can be used in the monitoring of aquatic ecosystems.

Genotoxicity and Oxidative Stress Evaluations in Juvenile African Catfish Clarias gariepinus Exposed to NPK Fertilizer

Juvenile African Catfish (also known as Sharptooth Catfish) Clarias gariepinus were exposed to 2.26, 4.52, and 11.30 mg/L NPK (15-15-15) fertilizer for 21 d followed by 7 d of recovery to assess the genotoxic effects of the fertilizer in erythrocytes. Biomarkers of oxidative stress were evaluated in the liver and gill tissues. The fertilizer induced micronuclei formation with maximum effects on day 7 in erythrocytes of individuals that were exposed to 4.52 and 11.30 mg/L NPK, and on day 14 in individuals exposed to 2.26 mg/L of the same fertilizer. The lipid peroxidation, glutathione reductase, and reduced glutathione values in the exposed fish increased, while the values of catalase, superoxide dismutase, and glutathione peroxidase decreased. There were mixed trends in the recovery patterns after the 7-d withdrawal from the fertilizer. Careful use of the fertilizer in the field is recommended to avoid toxicological effects on nontarget organisms.