Protein composition of cells, nuclei and chromatin from some radiosensitive and radioresistant mouse tissues.

The radioresistant tissues, heart, liver, lung and kidney, contain 2 to 15 times more protein per cell, nucleus and chromatin compared with the radiosensitive tissues, spleen and thymus. As determined by polyacrylamide gel electrophoresis, in the nuclear fraction and chromatin of radiosensitive tissues there is a deficit of high molecular weight (Mw greater than 20 000) non-histone proteins. It is suggested that the radiosensitivity of lymphoid cells, which die of interphase death a few hours after exposure to small doses of radiation, is closely correlated with this deficit in non-histone proteins.