title: Effect of caffeine on cell killing, mutation induction, DNA repair, and DNA synthesis after treatment with ethylnitrosourea.
abstract: The effect of caffeine on cell killing, mutation induction, DNA repair, and inhibition of DNA synthesis was investigated in a clonal derivative of M3-1 Chinese hamster cells after treatment with N-ethyl-N-nitrosourea (ENU). Caffeine enhanced cell killing but had no effect on the mutation frequency/viable cells for the two genetic markers, 6-thioguanine resistance and ouabain resistance. The removal of ethylated purine bases from DNA was as follows: most of the 3-ethyladenine was lost in 20 h (greater than 85%) and approximately 45% of the 7-ethylguanine was lost in 45 h, whereas 75--93% of the O6-ethylguanine was still present at this time. Caffeine did not seem to influence these rates significantly. The ENU-induced inhibition of DNA synthesis was reversed by caffeine. It is concluded that the potentiation of ENU-induced cell killing by caffeine is caused by the increased frequency of DNA replication past damaged sites in parental DNA.
mesh_terms: D000818:Animals; D001853:Bone Marrow; D002110:Caffeine / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D004260:DNA Repair / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects*; D005038:Ethylnitrosourea / Q000494:pharmacology*; D009154:Mutation; D009607:Nitrosourea Compounds / Q000494:pharmacology*
chemical_list: D009607:Nitrosourea Compounds; D002110:Caffeine; D005038:Ethylnitrosourea