Background: Protection of hematopoietic system has become a primary goal in the development of novel medical countermeasures against ionization radiation and radiotherapy. This study was to explore the role of rapamycin in normal tissues against radiation. Materials and Methods: Mice were pretreated with rapamycin by i.p. every other day for five times before 5 Gy or 8.5 Gy γ-ray whole bo...