The sensitivity of cells in exponential and stationary phases of growth to bleomycin and to 1,3-bis(2-chloroethyl)-1-nitrosourea.

Studies of EMT6 mouse tumour cells growing in vitro have shown that these cells become less sensitive to bleomycin as they pass from exponential growth into stationary phase. This result is the opposite of that recently reported by two other groups of workers using different cell systems, but in agreement with the results of a third group of workers. Results for 1,3-bis(2-chloroethyl)-1-nitrosourea, however, confirm the findings of other workers that cells become more sensitive to this agent as they pass into stationary phase.These findings are discussed with particular reference to discrepancies which appear to exist between various cell systems.