The relationship between the induction of SCEs and mutations in Chinese hamster cells. I. Experiments with hydrogen peroxide and caffeine.

Hydrogen peroxide (H2O2) and caffeine were examined for their capacity for inducing SCEs and mutations at the HPRT locus in V79 Chinese hamster cells. Although, under standard conditions, both substances induced SCEs neither caused gene mutations. The SCE induction by both H2O2 and caffeine is influenced by BrdUrd substitution. Whereas H2O2 also induces lesions leading to SCEs in normal DNA, the SCe induction by caffeine depends on the replication of BrdUrd-substituted DNA. In cells with BrdUrd-substituted DNA, H2O2 induces mutations at the HPRT locus parallel to its SCE induction, whereas caffeine in the presence of BrdUrd only has an influence on the SCE rate. It is shown that the experimental conditions of the two test systems can play a decisive role when contradictory results are obtained.