A protective effect of caffeine on drosophila larvae treated with methyl methanesulfonate.

Lethality induced in larval populations of Drosophila melanogaster was recorded after treatment with (1) caffeine, (2) MMS or (3) caffeine plus MMS. The mixture of caffeine plus MMS was less toxic than expected from the effects observed after treatment with either substance individually. It is postulated that in the combined treatment the caffeine, by inhibiting semiconservative DNA replication, allows for some additional time for repair of alkylated DNA by a repair pathway which is not sensitive to caffeine, possibly excision repair.