In Vitro Studies of the Sensitivity of Canine Bone-marrow Erythroid Burst-forming Units (BFU-E) and Fibroblast Colony-forming Units (CFU-F) to X-irradiation

The radiosensitivity of the early erythroid progenitor cells (BFU-E) and the progenitor cells of the stroma (CFU-F) in canine bone marrow was studied under steady-state conditions by in vitro irradiation with 280 kV X-rays. The dose-effect relationship for colony formation was determined for BFU-E obtained from the iliac crest marrow, and for CFU-F in bone marrow collected from the iliac crest and the humerus of adult beagles. The BFU-E were adequately stimulated with serum from lethally irradiated dogs to obtain a source of BPA (burst-promoting activity). The BFU-E proved to be extremely radiosensitive, and the survival curve was exponential (D0 = 15.3 +/- 1.8 cGy). We showed that buffy-coat leukocytes separated from bone marrow leukocytes obtained by aspiration were an optimum source of CFU-F. A curve was fitted to the data obtained for CFU-F obtained from the iliac crest or the humerus, resulting in D0 = 241 +/- 38 cGy and an extrapolation number n = 1.38 +/- 0.62 or D0 = 261 +/- 40 cGy and n = 1.04 +/- 0.42, respectively. According to these findings, and other published data, we conclude that the canine bone marrow BFU-E are presently the most radiosensitive hemopoietic cells detected among all hemopoietic cells of different mammals.