Effects of radiation on hematopoietic stroma.

The effects of x-irradiation on the CFU-S and on the hematopoietic stroma (HS-P) were studied and compared. Exposure to 300 rad reduced the CFU-S population to less than 1% of normal; by contrast more than 500 rad was required to detectably damage the HS-P. Although exposture to 500 rad did not detectably affect HS-P function, a second exposure to 500 rad as much as 4 weeks later did appreciably affect the HS-P. In addition, whereas the CFU-S returned to the pre-irradiation level within 6 weeks, the HS-P did not significantly recover. From these data we conclude that, with respect to the initial impact and exposure dose, HS-P is more radioresistant than CFU-S, but recovery from radiation induced damage of HS-P occurs slowly or does not take place.