2-HYDROXYADENINE, A MUTAGENIC FORM OF OXIDATIVE DNA-DAMAGE, IS NOT REPAIRED BY A GLYCOSYLASE TYPE MECHANISM IN RAT ORGANS

Oxygen radicals are known to play a role in causing cellular DNA damag e, which is involved in carcinogenesis. 8-Hydroxyguanine (8-OH-Gua) is a major form of oxidative DNA damage and is known as a useful marker of DNA oxidation. Recently, we found another type of oxidative DNA dam age, 2-hydroxyadenine (2-OH-Ade), which has a mutation frequency compa rable to that of 8-OH-Gua, We compared the repair activities for two t ypes of oxidative DNA damage, 8-OH-Gua and 2-OH-Ade, in 7-week-old mal e Sprague-Dawley (SD) rat organs. The repair activities were measured by an endonuclease nicking assay using 22 mer [P-32]-end-labeled doubl e-stranded DNA substrates, which contained either 8-OH-Gua (opposite C ) or 2-OH-Ade (opposite T or C). In all of the SD rat organs we studie d, the nicking activity for 2-OH-Ade was not detected, while that for 8-OH-Gua was clearly detected with the same conditions. Moreover, the 2-OH-Ade nicking activity was not induced in Wistar rat kidney extract s prepared after ferric nitrilotriacetate (Fe-NTA) treatment, which is known to increase 8-OH-Gua repair activity. These results suggest tha t 2-OH-Ade might not be repaired by the glycosylase type mechanism in mammalian cells. (C) 1998 Elsevier Science B.V. All rights reserved.