Oxidative stress biomarkers in Clarias gariepinus (Burchel, 1822) exposed to Microcystin-LR

Stress levels inflicted by microcystin-LR extracted from Microcystis aeruginosa were assessed by estimating the effects on the oxidative stress biomarkers in the liver, muscle and gill tissues of Clarias gariepinus. Microcystin-LR was administered to the fish by injection into their intra-peritoneal cavity. Microcystin-LR induced the activities of mainly Glutathione-S-Transferase (GST), Catalase (CAT) and Superoxide dismutase (SOD) in the liver on dose and temporal basis, while it inhibited the activities of Cytochrome P450 on temporal basis in the liver and gill. Results show that MC-LR significantly induced oxidative stress in the C. gariepinus. Findings show that 400 μg MC-LR/kg b.w. disrupted the antioxidant status of the fish without any external physical manifestation on the body. Microcystin-LR induced the activities of mainly GST, CAT and SOD in the liver on dose and temporal basis while it inhibited the activities of CYP450 on temporal basis in the liver and gill. The adopted MC-LR doses; particularly 400 μgMC-LR/kg b.w. inflicted stress on the fish without any external/physical manifestation. MC-LR impacted on the antioxidant enzymes in the fish; in the order of liver > gill > muscle. This research has provided empirical evidences that 400 μg MC-LR/kg b.w induced oxidative stress in C. gariepinus in less than a month of exposure. This adopted level of MC-LR can be used as a warning signal in natural water bodies and commercial C. gariepinus ponds.