Acetyl coenzyme A-dependent metabolic activation of N-hydroxy-3, 2'-dimethyl-4-aminobiphenyl and several carcinogenic N-hydroxy arylamines in relation to tissue and species differences, other acyl donors, and arylhydroxamic acid-dependent acyltransferases

The metabolic activation of several carcinogenic N-hydroxy (N-OH)-arylaminesby cytosolic S-acetyl coenzyme A (AcCoA)-dependent enzymes wasexamined in tissues and species susceptible to arylamine carcinogenesis.Comparisons of the AcCoA-dependent activity were also made withknown cytosolic arylhydroxamic acid-dependent acyltransferasesand with the ability of different acyl donors to mediate thebinding of N-OH-arylamines to DNA. With rat hepatic cytosol,AcCoA-dependent DNA binding was demonstrated for several [³H]N-OH-arylamines,in the order: N-OH-3, 2'-dimethyl-4-aminobiphenyl (N-OH-DMABF),N-OH-2-aminofluorene (N-OH-AF) > N-OH-4-aminobiphenyl >N-OH-N'-acetylbenzidine > N-OH-2-naphthylamine; N-OH-N-methyl-4-amino-azobenzenewas not a substrate. No activity was detected in dog hepaticor bladder cytosol with any of the N-OH-arylamines tested. Usingeither N-OH-DMABP or N-OH-AF and rat hepatic cytosol, activationto DNA-bound products was also detected with acetoacetyl- andpropionyl-CoA but not with folinic acid or six other acyl CoA's.However, p-nitro-phenyl acetate which is known to generate acetyl-enzymeintermediates effectively replaced AcCoA. Subcellular fractionationof rat liver showed that the AcCoA-dependent DNA-binding ofN-OH-DMABP with cytosol was 5 times greater than that obtainedwith the microsomal or mitochondrial/nuclear fractions. Furthermore,the cytosolic activity was insensitive to inhibition by theesterase/deacetylase inhibitor, paraoxon; while the activityof the other subcellular fractions was completely inhibited(>95%). AcCoA-dependent activation of N-OH-DMABP was alsodetected with rat tissue cytosols from intestine, mammary glandand kidney, which like the liver, are targets for arylamine-inducedtumorigenesis. Using N-OH-DMABP, AcCoA-dependent DNA-bindingactivity was also detected in the hepatic cytosols from severalspecies in the order: rabbit > hamster > rat, human >guinea pig > mouse. In contrast, the arylhydroxamic acid,N-OH-N-acetyl-DMABP, was not activated to a DNA-binding metaboliteby the hepatic cytosolic N, O-acyltransferase of any of thesespecies, thus suggesting that the AcCoA-mediated binding ofN-OH-DMABP results from the direct formation of N-acetoxy-DMABP.With N-OH-AF as the substrate, the AcCoA-dependent activationwas in the order: rabbit > guinea pig, hamster > mouse> human, rat. In contrast to the AcCoA-dependent activationof N-OH-AF, only very low N-OH-N-acetyl-4-aminobiphenyl-dependenttransacetylase and N-OH-N-acetyl-2-aminofluorene N, O-acyitransferaseactivity was detected in the hepatic cytosols for the human,guinea pig, and mouse. Selected inhibitors did not discriminatebetween the three acyltransferase activities in rat hepaticcytosol; and up to 40% inhibition was observed with 100 µM4-aminoazobenzene or pentachlorophenol. These studies indicatethat the AcCoA-dependent formation of reactive N-acetoxy arylaminesby cytosolic acetyltransferase(s) could serve as a major metabolicactivation pathway in several species, particularly those whichcannot utilize arylhydrox-amic acids as acyl donors for intramolecularN, O-acyltransfer or for intermolecular transacetylation ofN-OH-arylamines.