Relationship of Syrian inbred hamster acetylator genotype to the mutagenic activation of 2-aminofluorene.

The genetic constitution of mammalian enzymes involved in the metabolism of xenobiotics is one of the important factors responsible for large inter-individual differences in the rate of biotransformation and consequently the magnitude of genotoxic effects exerted in target tissues. The present study examines the mutagenic activation of 2-aminofluorene (AF) with hepatic post-mitochondrial (S9) preparations derived from homozygous rapid (Patr/Patr) acetylator and homozygous slow (Pats/Pats) acetylator Syrian inbred hamsters and its relationship to acetylator genotype. These hamster strains differ in their capacities for acetyl coenzyme A (AcCoA)-dependent, N-acetylation and O-acetylation of carcinogenic arylamines and their N-hydroxyarylamine metabolites. AF N-acetyltransferase activities determined in hepatic S9 fractions were 72.2 +/- 4.2 nmol/min/mg in rapid acetylator hamsters and 6.65 +/- 0.37 nmol/min/mg in slow acetylators, and were unaffected by the presence of 0.1 mM paraoxon. Mutagenic activation of AF was measured by reversion to histidine prototrophy in Salmonella typhimurium strain TA98. The metabolic activation of AF utilizing standard hepatic S9 preparations exhibited typical saturation kinetics that did not differ between acetylator genotypes. However, the addition of AcCoA to the standard S9 mix resulted in a dose-dependent reduction in the number of histidine revertants. In dose-response studies in which the concentrations of AF, AcCoA or S9 protein were varied, higher numbers of revertants were consistently generated with hepatic S9 derived from the slow acetylator compared to the rapid acetylator hamsters. These results indicate an acetylator genotype-dependent modulation of arylamine genotoxicity was reflected as a reduction in the levels of mutagenic metabolites generated in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the genotoxicity of gentian violet in bacterial and mammalian cell systems.

Previous studies indicate that gentian violet (GV), a triphenylmethane dye used in agriculture and human medicine, is a clastogen in vitro and a carcinogen in chronically exposed mice and rats. Data on its genotoxic activity, however, have been incomplete and partly contradictory. Mutagenesis and DNA damage experiments were conducted to re-evaluate the genotoxic potential of GV in both bacterial and mammalian cell systems. GV was mutagenic in Salmonella typhimurium tester strains TA97 and TA104, but there was little mutagenic activity detected in strains TA98 and TA100. A rat liver homogenate fraction (S9) tended to increase mutagenicity. The major microsomal metabolites of GV, pentamethylpararosaniline and N,N,N',N'-tetramethylpararosaniline were less mutagenic in TA97 and TA104, while N,N,N',N"-tetramethylpararosaniline was a weak mutagen in Salmonella. GV was not mutagenic in Chinese hamster ovary (CHO) cell strain CHO-K1-BH4, and was a questionable mutagen in CHO-AS52 cells. While GV produced DNA damage as measured by sedimentation of nucleotids derived from B6C3F1 mouse lymphocytes treated in vitro, no damage was found in lymphocytes isolated from mice dosed with GV. GV was also a weak producer of gene amplification in an SV40-transformed Chinese hamster cell line. The results indicate that GV is a point mutagen in bacteria; however, since similar exposure conditions produced weak mutagenic activity in mammalian cells, GV may be carcinogenic by virtue of its clastogenic activity.