The fluctuation test as a more sensitive system for determining induced mutation in L5178Y mouse lymphoma cells

Luria-Delbrück fluctuation tests for the determination of the spontaneous mutation rate to ouabain resistance incultured L5178Y mouse lymphoma cells gave values in the range 0.44 to 1.03 X 10(-7) mutants per cell per generation. Addition of very low, non-toxic, levels of EMS (0.1 mM) and MMS (0.012 mM) 30-48 h before plating in selective medium gave a highly significant increase in the number of ouabain-resistant mutants. Methods for the calculation of spontaneous and induced mutation rates are discussed and a method for the computation of induced mutation rates is described. It is suggested that the modified fluctuation test is a simpler and considerably more sensitive assay for mutagens than the conventional experimental design. Some of its limitations are discussed.