DIELDRIN INDUCES PEROXISOMAL ENZYMES IN FISH (SPARUS-AURATA) LIVER

We have previously described the increase of microsomal lipid peroxida tion and the appearance of new oxidized forms of Cu,Zn-superoxide dism utase in the liver of gilthead seabrams (Sparus aurata) injected with model xenobiotics, due to the increased production of reactive oxygen species (ROS) (Pedrajas et al., Chem. Biol. Interact., 1995). The effe cts of dieldrin and copper(II) on subcellular organelles directly rela ted with ROS production are now studied. Immature fish were injected w ith dieldrin and copper, 0.15 and 1.0 mg/kg, respectively. After 2 and 7 days, the livers were homogenized and the catalase and superoxide d ismutase activities were determined in subcellular fractions isolated by differential centrifugation: nucleus, mitochondria, light mitochond rial fraction (LMF), microsomes and cytosolic fraction. Peroxisomes we re isolated from LMF by discontinuous gradient centrifugation using Ny codenz. Changes in catalase and superoxide dismutase depended on the x enobiotic and affected to different subcellular fractions. Thus, the e ffects of copper(II) were mainly in nucleus and cytosol, whereas dield rin induced catalase and superoxide dismutase (up to 2.8-fold) prefere ntially in nucleus and LMF fractions. Dieldrin-injected fish showed al so highly increased activity of palmitoyl-CoA-oxidase (9.3-fold) and a nearly 2-fold increase in the protein concentration of the peroxisoma l fraction. The results described above suggest that the oxidative str ess previously detected for dieldrin in fish liver affects also to the peroxisomal enzymes. Copyright (C) 1996 Elsevier Science Inc.