Genetic effects induced in Saccharomyces cerevisiae by cyclophosphamide in vitro without liver enzyme preparations.

Cyclophosphamide induced forward mutation in Saccharomyces cerevisiae strain S288C and mitotic recombination in strains D3 and D5 but not in strain D4. The yeast cells were treated with the compound in phosphate buffer without recourse to metabolic activation protocols. Elevation of the treatment temperature increased the genetic activity of cyclophosphamide. Respiration-deficient isolates of strains S288C and D3 were more sensitive than the respiratory competent parent strains were for inducing forward mutation and mitotic recombination, respectively. Cyclophosphamide was incubated in phosphate buffer alone for increasing time intervals; strain D3 cells were added to aliquots for each time interval and incubated for an additional 30 min. The frequency of induced recombination increased as the time of compound incubation increased, showing that spontaneous degradation of cyclophosphamide to genetically active breakdown products was responsible for the genetic damage induced in the yeast cells.