Dose-dependent reduction of rat colon antioxidant enzyme activities and increased thiobarbituric acid reactive substances (TBARS) by ethidium bromide

Abstract

The effect of exposure to varying doses of ethidium bromide on the activities of rat colon antioxidant enzymes has been examined. The rats were divided into eight (08) experimental groups of 5 rats each. Group I rats served as the control, not exposed to ethidium bromide (EthBr). Group II rats were administered 5 mg ethidium bromide kg^-1body weight (bd wt),Group III 10 mg ethidium bromide kg^-1 body weight, Group IV 20 mg ethidium bromide kg-¹ body weight, Group V 40 mg ethidium bromide kg^-1body weight, Group VI 60 mg ethidium bromide kg^-1body weight, Group VII 80 mg ethidium bromide kg^-1 body weight, while rats in Group VIII were administered 100 mg ethidium bromide kg^-1 body weight. Treatment was done once weekly via gavage for 24 weeks. At the end of the exposure period, each rat was anaesthetized by halothane inhalation. Colon sections were collected, homogenized and the antioxidant enzyme activities in the homogenate    supernatants were determined. Relative to the control, colon catalase, superoxide dismutase and glutathione peroxidase showed evidence of significant (p ≤ 0.05) decrease in activity in rats exposed to ≥ 60, ≥ 20 and ≥ 60 mgethidium bromide kg-1body weight respectively. Compared to the control, thiobarbituric acid reactive substance (TBARS), as measured by malondialdehyde (MDA) levels were significantly (p ≤ 0.05) increased in rats exposed to ≥ 20 mg ethidium bromide kg^-1 bd wt.
There was a strong and significant negative correlation between ethidium bromide dose and colon catalase (r =-0.9823; p˂ 0.001), superoxide dismutase (r = -0.9107; p˂0.001) and glutathione peroxidase (r = -0.9772; p˂ 0.001) activities. There was a strong and positive correlation between ethidium bromide dose and colon MDA levels (r = + 0.9808; p˂ 0.001) but a strong negative correlation between colon catalase (r = - 0.9455; p˂ 0.001), superoxide dismutase (r = - 0.8707; p˂ 0.001) and glutathione peroxidase (r = - 0.9623; p˂ 0.001) and MDA level. Chronic oral exposure of albino rats to ethidium bromide at a dose above the nontoxic threshold of 10 mg kg^-1 body weight significantly impaired the activities of colon antioxidant enzymes.