Oxidative stress responses of juvenile catfish, Clarias gariepinus exposed to potassium dichromate at sublethal concentrations in south-eastern Nigeria

Abstract

The oxidative stress responses of Clarias gariepinus exposed to potassium dichromate at sublethal concentrations for 28 days were studied in 2017. Fish were exposed to 0.165, 0.0825 and 0.033 mg l⁻¹ corresponding to 1/10, 1/20 and 1/50 of the 96 h LC₅₀ of 1.65 mg l⁻¹. Haematological parameters of fish decreased in haemoglobin when compared with the control and there was reduction of mean corpuscular haemoglobin concentration, mean corpuscular haemoglobin and mean corpuscular volume in presence of potassium dichromate. Significant increase in white blood cells throughout the duration of exposure and decrease in lymphocytes were observed. The lipid peroxide levels were increased in test concentrations when compared with controls of liver and gill. The fish group was subjected to oxidative stress, because of lipid peroxidation in response to reactive oxygen species generation. Gill and liver tissues showed concentration and time dependent significant increase (p < 0.05) in values of malondialdehyde, catalase and superoxide dismutase, whereas there was reduced glutathione. Similarly, potassium dichromate enhanced levels of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase as both concentration and time dependent when compared with control. Micronuclei induction was highest (7.55) on day 14 in all concentrations in the peripheral blood cells. There were alterations in values of glutathione peroxidase, superoxide dismutase, and catalase during exposure and recovery periods.

Keywords: antioxidant enzyme, biochemistry, catfish, haematology