The Age Sensitivity of Epithelial Cells of Mouse Small Intestine

In vivo sensitivity variations during phases of cell cycle for jejunal crypt stem cells of mice are determined. Hydroxyurea blocked DNA synthesis and synchronized cells in crypts of mouse small intestine. Assays of number of regenerating crypts after exposing gut to 1,150 rads at varying intervals following hydroxyurea injection suggested cells were more resistant in late S-phase of cell cycle. Sensitivity to radiation apparently increased as cells passed through S-phase for first time after hydroxyurea treatment. Redistributing age density and changing population radiosensitivity should be considered in radiotherapy if gut is exposed after hydroxyurea treatment.