Functional changes in the vascularity of the irradiated rat femur. Implications for late effects.

Early and late changes in the extraction of 125I antipyrine was investigated in the rat femur after local irradiation with single doses of 5 to 25 Gy. The extraction of antipyrine by bone was generally reduced after irradiation, with the greatest effect being found 3 months after treatment. However, the effect was transient and by 7 months after less than or equal to 20 Gy, antipyrine extraction was similar to that in the normal femur. Extraction was still reduced after 25 Gy. The first significant reduction in dry bone weight occurred 7 months after 15, 20 and 25 Gy. The fall in the calcium and phosphorus content of bone was similar to that of the dry bone weight. Calcium/phosphorus ratio was not modified in irradiated bone. The likely role of the vascular changes in the subsequent development of bone atrophy is discussed.