Cytosolic Acetyl Transfer and N-Deacetylation Associated with the Metabolism of Carcinogenic 2,4-Diaminotoluene in Rat Liver.

Abstract

Acetyl transfer and N-deacetylation associated with the metabolism of carcinogenic 2,4-diaminotoluene (2,4-DAT) were examined by detecting the products formed during the incubation of 2,4-DAT and its known urinary metabolites with the liver cytosol fraction from male Wistar rats. Data obtained from the incubation of 4-acetylamino-2-aminotoluene (4AA2AT) with the liver cytosol in the presence of 2,4-diaminobenzoic acid (2,4-DABA) indicated that the cytosol catalyzes the acetyl transfer between 4AA2AT and 2,4-DABA to produce 2,4-DAT and 2-acetylamino-4-aminobenzoic acid (2AA4ABA). The cytosol also catalyzed the acetyl transfer between 2,4-diacetylaminotoluene (2,4-DAAT) and 2,4-DABA to produce 2-acetylamino-4-aminotoluene (2AA4AT) and 2AA4ABA. Without 2,4-DABA, the cytosol catalyzed the N-deacetylations of 4AA2AT and 2,4-DAAT to produce 2,4-DAT and 2AA4AT. 2AA4AT was inactive for both the N-deacetylation and the acetyl transfer. 2,4-DAT itself was N-acetylated to 4AA2AT by incubation with acetyl-CoA, but 2AA4AT and 2,4-DAAT were not detectable in the incubation product. However, both 2AA4AT and 4AA2AT were N-acetylated to 2,4-DAAT by incubation with acetyl-CoA. These findings suggest that 2,4-DAT is reproduced either by the N-deacetylation of 4AA2AT or by the acetyl transfer between 4AA2AT and 2,4-DABA in the metabolism of 2,4-DAT and further suggest that 2,4-DAAT is produced by the acetyl-CoA-dependent N-acetylation of 4AA2AT; 2AA4AT is produced either by the N-deacetylation of 2,4-DAAT or by the acetyl transfer between 2,4-DAAT and 2,4-DABA. Based on these results, the metabolic pathway of 2,4-DAT in the rat is proposed.