REACTIONS OF GLUTATHIONE WITH CARCINOGENIC ESTERS OF N-ARYLHYDROXAMIC ACIDS

摘要

The nitrenium ions 7a and 7b derived from hydrolysis of N-(sulfonatooxy)-N-acetyl-2-aminofluorene (1a) and N-(sulfonatooxy)-N-acetyl-4-aminobipheny (1b) are trapped by glutathione anion (GS(-)) with selectivity ratios, k(gs)-lk(s), of 8200 +/- 600 M(-1) and 300 +/- 15 M(-1), respectively. Since k(s) is known for both of these ions under our reaction conditions, k(gs)- can be calculated. For 7a, k(gs)- is 6.3 x 10(8) M(-1) s(-1), and for 7b, k(gs)- is 1.8 x 10(9) M(-1) S-1 Under physiological conditions (50-100 mu M GS(-)) neither ion would be efficiently trapped by GS(-). Some of the GSH adducts isolated in this study (4 from 1a, 11 and 12 from 1b) are not derived from nitrenium ion trapping. They arise from GS- trapping of the quinol imines 8a and 8b, which are the initial products of trapping of 7a and 7b by H2O. This reaction is very efficient at physiological GS(-) Concentrations and could lead to significant GSH depletion in vivo. Although it has been known for some time that quinol imines such as 8a and 8b are major hydrolysis products of carcinogenic esters of N-arylhydroxylamines and N-arylhydroxamic acids, no physiological role has been previously suggested for these materials.