IDENTIFICATION OF -YL)-2-AMINO-3,8-DIMETHYLIMIDAZO[4,5-F]QUINOXALINE 3',5'-DIPHOSPHATE, A MAJOR DNA ADDUCT, DETECTED BY NUCLEASE P1 MODIFICATION OF THE P-32 POSTLABELING METHOD, IN THE LIVER OF RATS FED MEIQX

The carcinogenic heterocyclic amine 2-amino-3,8-dimethyl-imidazo[4,5-f ]quinoxaline (MeIQx) is widely distributed in cooked foods. The nuclea se P1 method increased the sensitivity of the standard P-32-postlabeli ng analysis about 1000-fold for detection of MeIQx - DNA adducts. The recovery of MeIQx - DNA adducts by the nuclease P1 method was determin ed to be about 50% using liver DNA of a rat treated with [C-14]MeIQx i ntragastrically. By the nuclease PI method rive adducts were detected in the liver DNA of rats fed MeIQx and two of them, including the most abundant one, were identified as MeIQx-deoxyguanosine adducts by comp arison with the adducts formed in in vitro reactions of toxy-2-amino-3 ,8-dimethylimidazo[4,5-f]quinoxaline with the four 2'-deoxyribonucleot ides. The most abundant adduct in vivo was identified as N2-(deoxyguan osin-8-yl)-MeIQx 3',5'-diphosphate (3',5'-pdGp-C8 - MeIQx). MeIQx-DNA adduct levels in human tissues could be determined by the nuclease P1 modification of the P-32-postlabeling method in combination with HPLC, and thus provide information on the roles of MeIQx in human carcinoge nesis.