Distribution of²²⁶Ra in the Bones of Mice

Longterm biologic investigations with incorporated bone-seeking radionuclides are mainly directed at the production of osteosarcomas ( FINKEL et coll. 1969, HUG et coll. 1969, NILSSON 1970, KLENER et coll. 1973). The incidence of bone tumours further depends on the applied dose and the method of radionuclide administration. In mice these growths are predominantly localized in the axial skeleton and long bones (EVANS et coll. 1944, HOPKINS et coll. 1966, SVOBODA et coll. 1971). MARSHALL & FINKEL (1959) in endeavouring to explain the differences in localization of osteogenic sarcomas after incorporation of 'Ca, 'Sr and 'Ra carried out a comprehensive autoradiographic dosimetry of the bones of mice. The conclusions of this investigation have become topical recently as possible sites of osteosarcomas are becoming more specific. This was also aided by ICRP publication No. 11 (1968) and recent experiments by BARNES et coll. (1970) and LOUTIT & VAUGHAN (1971) designed to elucidate the nature of osteoprogenitive cells. Specification of the skeletal regions where the cells with the highest proliferative potential are present and where the hazards of carcinogenesis could occur requires a more detailed analysis of the nonuniform distribution of activity and dose. The present experiments were designed to determine the initial deposition of 226Ra in different regions of the