Long-term Effects of Local Irradiation of the Marrow on Erythron and Red Cell Function

Changes in erythron and RE cell function were examined in the marrow of the rabbit after 250-5000 R of localized irradiation by comparing the amount of ⁵⁹Fe and ^99mTc sulfur colloid concentrated in the irradiated tibiofibula to that in the unirradiated control. At all levels of irradiation, there was immediate and severe loss of erythron function while RE cell activity remained nearly intact. Erythron function showed prompt partial recovery to a maximum level at approximately 8 days but with doses greater than 1000 R there was a secondary decline to 20 per cent of normal during the next 8 weeks. After 15 days, RE cell function had decreased to the same level as the erythron and subsequently fell in parallel with it. After 15 months, the marrow showed a secondary recovery of both RE cell and erythron function to 50 and 66 per cent of normal. The results of these experiments suggest that radiocolloid photoscans of the marrow showing decreased or absent RE cell activity will reflect a similar degree of erythropoietic damage if the studies are obtained weeks or months following radiation therapy.