TY - JOUR

T1 - Formation of DNA adducts by the food mutagen 2-amino-3,4,8-trimethyl-3h-imidazo [4,8-f]quinoxaline (4,8-dimeiqx) in vitro and in vivo. identification of a N-(2'-deoxyguanosin-8-yl)-4,8-dimeiqx adduct

AU - Frandsen, Henrik

AU - Grivas, Spiros

AU - Turesky, Robert J

AU - Andersson, Rolf

AU - Dragsted, Lars Ove

AU - Larsen, John Christian

N1 - (Ekstern)

PY - 1994

Y1 - 1994

N2 - The covalent binding of the mutagenic N2-hydroxy metaboilte of the food mutagen 2-amino-3,4,8-trimethyl-3H-lmldazo[4,5-f]quinoxaline (4,8-DiMeIQx) to 2'-deoxy-nudeosides and DNA was investigated in vitro and in vivo. N2-Hydroxy-4,8-DiMeIQx reacted to a small extent spontaneously with 2-deoxyguanosine. However, acetylatlon of N2-hydroxy-4,8-DiMeIqx with acetic anhydride to form the N2-acetoxy derivative prior to reaction with 2-deoxyguanosine resulted in much higher yield of adduct. N2-Acetoxy-4,8-DiMeIQx did not form adducts with 2'-deoxy- adenosine, 2'-deoxycytldlne or 2'-deoxythymldlne. The adduct formed between the N metabolite of 4,8- DiMeIQx and 2-deoxyguanosine was analysed by mass spectrometry and NMR spectroscopy and the structure of the adduct was shown to be N2-Acetoxy-4,8-DiMeIQx. N2-Acetoxy-4,8-DiMeIQx. reacted with calf thymus DNA and formed a covalently bound 4,8-DiMeIQx residue, which could not be removed by repeated precipita tions or solvent extractions. The 4,8-DiMeIQx-DNA was hydrolysed enzymatically with nuclease P1/acid phosphat ase and HPLC analysis showed that 70% of the bound mutagen was recovered as N2-Acetoxy-4,8-DiMeIQx. An additional minor adduct accounting for ∼15% of the bound mutagen showed UV spectral characteristics similar to N2-(2'-deoxyguanosin-8-yl)-4,8-DiMeIQx and is probably an undigested oligomer. 32P-Postlabelling analysis of calf thymus DNA modilied with 4,8-DiMeIQx in vitro and liver DNA from rats dosed with 50 mg/kg 4,8-DiMeIQx showed a similar adduct pattern. In both samples N2-(2'- deoxyguanosln-8-yl)-4,8-DiMeIQx accounted for 60-70% of the bound mutagen. Thus, these results show that 4,8-DiMeIQx similar to other heterocyclic amines form adducts with C-8 of guanine both in vitro and in vivo via Its N2-OH metabolite.

AB - The covalent binding of the mutagenic N2-hydroxy metaboilte of the food mutagen 2-amino-3,4,8-trimethyl-3H-lmldazo[4,5-f]quinoxaline (4,8-DiMeIQx) to 2'-deoxy-nudeosides and DNA was investigated in vitro and in vivo. N2-Hydroxy-4,8-DiMeIQx reacted to a small extent spontaneously with 2-deoxyguanosine. However, acetylatlon of N2-hydroxy-4,8-DiMeIqx with acetic anhydride to form the N2-acetoxy derivative prior to reaction with 2-deoxyguanosine resulted in much higher yield of adduct. N2-Acetoxy-4,8-DiMeIQx did not form adducts with 2'-deoxy- adenosine, 2'-deoxycytldlne or 2'-deoxythymldlne. The adduct formed between the N metabolite of 4,8- DiMeIQx and 2-deoxyguanosine was analysed by mass spectrometry and NMR spectroscopy and the structure of the adduct was shown to be N2-Acetoxy-4,8-DiMeIQx. N2-Acetoxy-4,8-DiMeIQx. reacted with calf thymus DNA and formed a covalently bound 4,8-DiMeIQx residue, which could not be removed by repeated precipita tions or solvent extractions. The 4,8-DiMeIQx-DNA was hydrolysed enzymatically with nuclease P1/acid phosphat ase and HPLC analysis showed that 70% of the bound mutagen was recovered as N2-Acetoxy-4,8-DiMeIQx. An additional minor adduct accounting for ∼15% of the bound mutagen showed UV spectral characteristics similar to N2-(2'-deoxyguanosin-8-yl)-4,8-DiMeIQx and is probably an undigested oligomer. 32P-Postlabelling analysis of calf thymus DNA modilied with 4,8-DiMeIQx in vitro and liver DNA from rats dosed with 50 mg/kg 4,8-DiMeIQx showed a similar adduct pattern. In both samples N2-(2'- deoxyguanosln-8-yl)-4,8-DiMeIQx accounted for 60-70% of the bound mutagen. Thus, these results show that 4,8-DiMeIQx similar to other heterocyclic amines form adducts with C-8 of guanine both in vitro and in vivo via Its N2-OH metabolite.

UR - http://www.scopus.com/inward/record.url?scp=0028073449&partnerID=8YFLogxK

U2 - 10.1093/carcin/15.11.2553

DO - 10.1093/carcin/15.11.2553

M3 - Journal article

C2 - 7955105

AN - SCOPUS:0028073449

VL - 15

SP - 2553

EP - 2558

JO - Carcinogenesis

JF - Carcinogenesis

SN - 0143-3334

IS - 11

ER -