INDIVIDUAL LEVELS OF ACTIVITY OF O6-ALKYLGUANINE-DNA ALKYLTRANSFERASEIN MONKEY GASTRIC-MUCOSA DURING CHRONIC EXPOSURE TO A GASTROCARCINOGEN N-ETHYL-N'-NITRO-N-NITROSOGUANIDINE

The activity of a DNA repair enzyme, O6-alkylguanine-DNA alkyltransfer ase (AGT), was studied in gastric mucosa of 15 Macaca fascicularis mon keys before and during chronic oral exposure to the ethylating carcino gen N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in order to investigate possible causes of inter-individual differences in susceptibility to its gastrocarcinogenic effect. A wide range of AGT activity (307-1903 fmol/mg protein, mean 695) was found before treatment and it decreased during the first year of exposure (means 627, 479 and 452 fmol/mg pro tein respectively at 6, 12 and 18 months after the beginning of the ex periment). The carcinogenesis study is under way and to date four monk eys with low initial AGT level in gastric mucosa died of gastric cance r. The relevance of AGT level measurement for prediction of individual susceptibility to ENNG is discussed.