Antipain, but not cycloheximide, suppresses radiation transformation when present for only one day at five days post-irradiation.

It has previously been observed that protease inhibitors suppress radiation transformation in vitro. In the experiments reported here, it was observed that a 24 h treatment with the protease inhibitor antipain at five days post-irradiation was sufficient to significantly suppress radiation transformation. Comparable experiments performed with cycloheximide, an inhibitor of protein synthesis, showed that this metabolic inhibitor could suppress radiation transformation when present immediately following the X-ray exposure but not when present for one day at five days post-irradiation. These results suggest that antipain is suppressing an ongoing cellular process occurring in response to X-irradiation.