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DNA BREAKS CAUSED BY MONOCHROMATIC 365 nm ULTRAVIOLET‐A RADIATION OR HYDROGEN PEROXIDE and THEIR REPAIR IN HUMAN EPITHELIOID and XERODERMA PIGMENTOSUM CELLS
Author(s) -
Peak Jennifer G.,
Pilas Barbara,
Dudek Edward J.,
Peak Meyrick J.
Publication year - 1991
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1991.tb02007.x
Subject(s) - xeroderma pigmentosum , hydrogen peroxide , irradiation , chemistry , microbiology and biotechnology , catalase , dna damage , dna , photochemistry , biology , biochemistry , antioxidant , physics , nuclear physics
The induction and repair of DNA single‐strand breaks (SSB) assayed by alkaline filter elution was compared in human epithelioid P3 and xeroderma pigmentosum (XP) cells exposed to monochromatic 365‐nm UV‐A radiation and H 2 O 2 . Initial yields of SSB were measured with the cells held at 0.5°C during exposure. The yield from exposure to 365‐nm radiation was slightly greater in XP than in P3 cells, whereas H 2 O 2 produced more than three times as many SSB in P3 compared with XP cells. o ‐Phenanthroline (50 m M ) markedly inhibited the yields of SSB induced in XP cells by H 2 O 2 , but had no effect on those produced by 365‐nm UV‐A. These results are consistent with the fact that P3 cells, unlike XP cells, have undetectable levels of catalase. The measured production of trace amounts of H 2 O 2 by the actual 365‐nm UV‐A exposures was not sufficient to account for the numbers of breaks that were observed. Single‐strand breaks produced by both agents were completely repaired after 50 min in P3 cells, as were H 2 O 2 ‐induced SSB in XP cells. However, 25% of the 365‐nm UV‐A‐induced SSB in XP cells remained refractory to repair after 60 min. The results show that SSB produced by these two agents are different and that 365 nm radiation produces most SSB in cells by mechanisms other than by production of H 2 O 2 .