Acyl CoA oxidase is the most suitable marker for hepatic peroxisomal changes caused by treatment of F344 rats with di(2-ethylhexyl)phthalate.

Hepatic peroxisomal changes, caused by treating male Fischer 344 rats with di(2-ethylhexyl)phthalate, were examined by measuring activities of enzymes involved in peroxisomal beta-oxidation, catalase and levels of the 80,000 Da peroxisome proliferation-associated polypeptide. Acyl CoA oxidase activity was increased 2.5-fold after 1 day, and 8-fold after 14 days. Enoyl CoA hydratase activity increased 2-fold after 2 days and 6-fold after 14 days. There were no significant increases in hydroxyacyl CoA dehydrogenase or catalase activities after 3 days of treatment. Thus acyl CoA oxidase activity was the most sensitive marker of early peroxisomal changes. The apparent no-observable-effect level for this change was 0.06 g/kg/day.