Acute and chronic toxicity of aromatic amines studied in the isolated perfused rat liver

Abstract

Isolated perfused livers from male Wistar rats were used to study acute and chronic toxic effects of carcinogenic aromatic amines. We investigated the hypothesis that aromatic amines can generate reactive oxygen species as part of their metabolism. Concentrations of 200-400 microM of 2-acetylaminofluorene (AAF), N-hydroxy-AAF, trans-4-acetylaminostilbene (AAS), N-hydroxy-AAS, and N-hydroxy-2-acetylaminophenanthrene in the recirculating perfusate were not toxic in a 2-hr exposure time as assessed by LDH efflux into the perfusate, glutathione excretion into bile, and changes of the beta-hydroxybutyrate/acetoacetate ratio in the perfusate. N-Acetoxy-AAF, however, was severely toxic. Menadione served as a positive control. It is concluded that exposures likely to occur in carcinogenicity studies with these aromatic amines will not be acutely toxic. In additional experiments the isolated perfused liver system was used to demonstrate chronic effects generated by feeding the carcinogenic dose of 0.02% AAF for up to 12 weeks. The following alterations were observed in livers from AAF-fed animals. excretion of glutathione into bile is drastically reduced after 5 or more weeks, increasingly less glucose is released into the perfusate, and oxygen consumption is constantly increased by 20% after 3 and more weeks of AAF feeding. Whereas the total glutathione level increased with time in homogenates of such livers, it decreased in the mitochondrial fraction. The results are interpreted as adaptive responses to chronic toxic effects of AAF which may be related to the promoting properties of this carcinogen.