INGESTION OF SUBLETHAL LEVELS OF IRON SULFATE BY AFRICAN CATFISH AFFECTS GROWTH AND TISSUE LIPID-PEROXIDATION

In order to determine the effect of increased iron intake on growth an d lipid peroxidation criteria in fish, African catfish (Clarias gariep inus) juveniles of mean weight 32.25 g were fed a ration of 2% body-we ight per day, for 5 weeks on fishmeal-based diets containing either 66 3.5 +/- 56.4 or 6354.4 +/- 70.3 mg iron per kg dry diet (supplied as F eSo(4) . 7H(2)O). Ingestion of the higher dietary iron ration resulted in suppressed growth (p < 0.05) in catfish, implying that the metal w as supplied at toxic levels, though tissue concentrations of the metal were unaffected by dietary regime (p > 0.05 for muscle, liver and pla sma) and haematocrit values were not significantly different between t reatments (p > 0.05). Despite this, concentrations of the lipid peroxi dation product malondialdehyde (MDA) in liver and heart increased conc omitant with dietary iron dose (p < 0.05) indicating heightened oxidat ive stress in catfish consuming diets high in iron. Additionally, assa yed levels of the fat-soluble antioxidant vitamin, vitamin E (alpha-to copherol) were significantly depleted (p < 0.001) in livers from these fish, thus demonstrating tocopherol use under conditions of dietary o xidant overload and revealing hepatic vitamin E status to be a useful bioindicator of chronic iron exposure. (C) 1997 Elsevier Science B.V.