Methyl methanesulphonate mutagenesis in L5178Y mouse lymphoma cells.

The alkylating agent MMS was toxic to mouse lymphoma L5178Y cells and decreased their growth rate. A dose-dependent induction of thioguanine- and thymidine- but not ouabain-resistant variants was observed. The prolonged period for expression of thioguanine-resistant variants observed with other mutagens was also found in these studies. A comparison of MMS and EMS showed that MMS on a molar basis was approximately 10 times more toxic than EMS. With mutation, however, when evaluated at equal levels of cell killing MMS and EMS induced the same number of thymidine-resistant variants. For thioguanine-resistant variants MMS was approximately 10-fold less efficient than EMS, while for ouabain-resistance MMS, unlike EMBS, produced no variants at all. The ouabain results were further compared with positive results obtained using a modified Luria--Delbrück fluctuation test.