N-Methyl-N-nitrosourethane and ~-Propiolactone 1.2

ABSTRACT-The toxic and mutagenic effects of the alkylatlng agents N-methyl-N-nltrosourethane (MNUT) and,B-proplolactone (BPL) were quantitatively measured In human Iymphoblasts and Salmonella typhlmurlum. Forward mutation to 6-thloguanlne re-sistance was measured In the human Iymphoblasts, and forward mutation to B-azaguanlne resistance was measured In the bac-terial cells after equlgeneratlonal (1.5 doubling times) exposures. In both systems, the Induced mutant fraction rose linearly as a function of concentration for BPL and was blphaslc for MNUT. The responses of the two assay systems to eight alkylatlng agents were compared. The exposure of the cells to each alkylallng agent was calculated as exposure concentration multi-plied by the lime of exposure, and allowance was made for the decomposition of the alkylallng agents during exposure (Integral exposure). Human cells were 2.5-13 times more sensitive tha