The ability of liver extracts from different-aged rats to repair 'mis-instructive' and 'non-instructive' lesions of DNA

  • Pardini C
  • Mariani L
  • Voliani M
 et al. 
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The ability to repair 'mis-instructive', O6-methylguanine, and 'non-instructive', AP sites, DNA lesions in Fischer 344 rat livers at various ages was determined. Different behaviours were observed. While the AP-endodesoxyribonuclease enzymes displayed a high constant level throughout the animals' lifetime, the O6-methylguanine-DNA methyltransferase activity presented a stepwise modulation (DNA normalization of results): the O6-MT activity significantly increased within the first month of animal life and enhanced again after 6 months reaching a maximum plateau in the 12-18-month-old animals. Thereafter a net significant decrease of O6-MT enzyme was detected in the 24-month-old group. While the repair of the widely formed AP sites appeared uniformly efficient like 'house keeping' functions, the removal of the rare precancerous O6-methylguanine is age-dependent indicating a decreased protection of the youngest and oldest animals against this 'mis-instructive' damage. However, any extrapolation of the age-associated cancer risk needs further assessment. © 1992.

Author-supplied keywords

  • (Rats)
  • Apurinic/apyrimidinic sites
  • DNA damage
  • O6-Methylguanine

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  • C. Pardini

  • L. Mariani

  • M. Voliani

  • G. Rainaldi

  • L. Citti

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