Distribution of 32P, 45Ca, 85Sr and 133Ba As a Function of Age in the Mouse Skeleton

Abstract

The main object of this study has been to provide quantitative information on the distribution and retention of 32P, 45Ca, 85Sr and 133Ba in the mouse skeleton as a function of age at the time of injection, At 24 hr after intraperitoneal (i.p.) injection into 8-week old mice the distribution of the four radionuclides throughout the skeleton was essentially identical. In the case of 85Sr, however, the skeleton accumulated about 90% of the total body activity at this time, whereas for 32P the amount was only about 40%. The levels of accumulation of activity by the bones depended upon the age of the animals at the time of injection. Thus at 24 hr after i.p. injection of 85Sr into 3 and 26-week old animals the concentration of 85Sr in the bones varied by factors of less than 1.5 and 5 respectively. These differences were attributed mainly to the degree of vascularisation and the surface area available for absorption in individual bones. The relative concentrations of activity in the bones changed considerably with time after injection due mainly to varying rates of loss of activity from different bones. In older animals the levels of activity in the various bones became more uniform with time but in the youngest mice injected (3 weeks old) concentrations in individual bones varied by about a factor of 9 by 128 days after injection. It was also shown that in the mouse there is no significant release of 90Y formed from 90Sr deposited in bone.