Effect of Terephthalic Acid on the Activities of p-Dimethylaminoazobenzene Metabolizing Enzymes in Rat Liver

抄録

The reductase and demethylase activities of rat liver fed the p-dimethylaminoazobenzene (DAB) diet with or without 2.5% disodium terephthalate (Na₂TPA) were measured to clarify the participation of terephthalic acid (TPA) in DAB metabolism. Male rats of Wistar strain were fed the three different experimental diets for 2 or 4 weeks, which were supplemented with 0.06% DAB, with 2.5% Na₂TPA and 0.06% DAB, or with 2.5% Na₂TPA (DAB, TPA plus DAB or TPA diets, respectively). Although neither reductase nor demethylase activities were increased by the TPA diet feeding, they were maintained by TPA plus DAB diet when compared with the notable decrease by DAB feeding. From these findings, it was suggested that Na₂TPA did not activate these enzymes, but prevented the decline of their activities induced by DBA. The effects of two TPA derivatives, dimethyl terephthalate (DMT) and β-hydroxyethyl terephthalate (BHET), on these enzyme systems were also studied. DMT elevated the reductase activity only when it supplemented the basal diet. BHET fairly increased the reductase activity when it was given with DAB. Both derivatives were not superior to Na₂TPA in their efficacies. Furthermore, the content of protein bound aminoazo dyes in the liver of rat fed DAB plus TPA or BHET (but not DMT) were much lower than the content on the DAB diet feeding. The potentiating effect of TPA on DAB metabolism may be supported by this result.