Changes in liver enzyme activity in the teleost Sparus aurata in response to cadmium intoxication

Enzyme activity modulation by cadmium in the liver of the teleost fish Sparus aurata was investigated in vivo following 3 and 6 days of CdCl2 administration (2.5 mg/kg body wt). The specific activities of the mitochondrial enzymes NAD-isocitrate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase were stimulated by approximately 20% after 3 days administration and were further increased (by about 40%) after 6 days treatment. In comparison with these enzymes, the activities of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) in mitochondria were less stimulated after the two indicated intervals of treatment. Cadmium significantly reduced the activities of liver cytoplasmic GOT and GPT while a simultaneous increase occurred in the serum activities of these same enzymes. The activity of liver NADPH-cytochrome P450 reductase was stimulated by 25 and 40% after 3 and 6 days cadmium intoxication, respectively. Lastly, the antioxidant enzymes glutathione peroxidase and glutathione reductase in liver and catalase in both liver and blood were strongly reduced after 3 and 6 days cadmium administration. These data suggest that cadmium in fish hepatocytes alters cell membrane structure and concomitantly induces some perturbation in the integrity of the mitochondrial membrane.