Carcinogenesis, Vol 19, 809-812, Copyright © 1998 by Oxford University Press
M Dusinska, Z Kovacikova, B Vallova and A Collins
Because lung cells are inevitably exposed to chemicals, drugs and mineral
particles, they are appropriate target cells for investigating effects of
environmental toxins. We have studied alveolar macrophages and epithelial
type II pneumocytes freshly isolated from the rat lung, using the comet
assay to detect DNA damage (strand breaks and oxidized bases) in individual
cells after treatment with the pesticide paraquat. The background level of
strand breaks is five times higher in freshly isolated pneumocytes than in
alveolar macrophages. This difference remains even after 48 h of in vitro
culture and therefore probably does not reflect trauma suffered during
isolation. In contrast, endogenous formamidopyrimidine glycosylase- and
endonuclease III-sensitive sites, which are specific indicators of
oxidative damage, are present in freshly isolated alveolar macrophages but
not in pneumocytes, reflecting the high metabolic activity of macrophages
and their defensive role. Both cell types are exquisitely sensitive to
strand breakage by paraquat. In addition, specific base oxidation is
detected after 24 h of treatment with paraquat, especially in alveolar
macrophages. Susceptibility to DNA damage, rather than lipid peroxidation,
is likely to be the cause of paraquat-induced death in these cells. The
relatively high level of endogenous damage in pneumocytes suggests that
these cells are inefficient at DNA repair, which would be consistent with
their probable role as the principal progenitors of lung cancer.
ARTICLES
Responses of alveolar macrophages and epithelial type II cells to oxidative DNA damage caused by paraquat
Institute of Preventive and Clinical Medicine, Bratislava, Slovak Republic. dusinska@upkm.sanet.sk
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