Abstract
Irradiation of cultured murine mammary carcinoma (M 8013 S) cells during incubation in buffers of different pH showed a decrease in radiation sensitivity with lower pH. The presence of CCCP (carbonylcyanide-3-chlorophenylhydrazone) during incubation had no effect at pH values above 7·5, but at lower pH there was a marked increase in radiation sensitivity. The effects of CCCP are presumably related to its proton-conducting properties.