Relative radiosensitivity of bone tumor induction among beagles as a function of age at injection of 239Pu or 226Ra

A comparison was made of the response to induction of skeletal malignancy from exposure of beagles to monomeric Pu-239 Or to Ra-226 as juveniles (3 mo of age), young adults (1.5 y of age), or mature adults (5 y of age). This indicated that of these age groups, animals injected as young adults are most sensitive per Gy of average skeletal dose evaluated at 1 y before death. Dogs exposed either as juveniles or as mature adults appeared to be less sensitive. Relative radiosensitivities (RRS) of juvenile and mature beagles ranged between about 0.3 and 0.7 that of dogs injected as young adults. Mean values of RRS for both radionuclides were about 0.5, but RRS values derived from dogs given monomeric Pu-239 appeared to be most reliable and were 0.27 +/- 0.09 for dogs injected as juveniles and 0.41 +/- 0.13 for animals exposed as mature adults.