Changes in catalase, glutathione peroxidase and glutathione-S-transferase activities in the liver of newts exposed to 2-methyl-4-chlorophenoxyacetic acid (MCPA).

Activities of catalase, glutathione peroxidase (GSH-Px) and glutathione-S-transferase (GST) were measured in livers of the crested newt (Urodele Amphibian) after 16 days of percutaneous exposure to the herbicide Agroxone 3, a commercial formulation of 2-methyl-4-chlorophenoxyacetic acid (MCPA) containing 25% MCPA as sodium salt and 75% wetting and dispersing ingredients. Animals of both sexes were exposed to 800 p.p.m. of the active ingredient. There was a three-fold increase in catalase and a clear enhancement of GSH-Px in the MCPA-exposed animals of both sexes. A sex-dependent effect of MCPA was observed on GST activity, which increased significantly in female newts only. Similar liver enzyme changes were observed in female newts, and not in males, given the hypolipidaemic drug clofibrate (13 mg/animal/day, by gavage, for 8 days), which is structurally related to phenoxyherbicides. These findings indicate that the crested newt is sensitive to the hepatic effects of the peroxisome proliferators.