The Microdistribution and Retention of Injected 239 Pu on Trabecular Bone Surfaces of the Beagle: Implications for the Induction of Osteosarcoma

Abstract

The relationship between skeletal remodeling and the microdistribution and retention of 239Pu on trabecular bone surfaces of the beagle, and the contribution of these parameters to the nonuniform skeletal distribution of 239Pu-induced osteosarcomas were studied. Young adult beagles were administered single i.v. injections of .apprx. 0.016 .mu.Ci/kg monomeric 239Pu citrate and sacrificed at various times to 1 yr after injection. The 239Pu concentration on trabecular bone surfaces was determined by counting fission fragment tracks in neutron-induced autoradiographs produced from thick (.apprx. 400 .mu.m) bone sections. The rate of trabecular bone formation was calculated from an UV microscopic analysis of fluorescent tetracycline labels. The lumbar vertebra, pelvis and proximal humerus, each of which exhibits a high incidence of 239Pu-induced osteosarcoma, had a high initial concentration of 239Pu on the trabecular surfaces (.apprx. 7-8 pCi/cm2) and a relatively high rate of trabecular bone formation. The 239Pu concentration at these sites decreased to .apprx. 2-3 pCi/cm2 at the end of the 1st yr. The proximal ulna and distal humerus, skeletal sites with a low tumor incidence, had a low initial concentration of 239Pu on their trabecular surfaces (.apprx. 1-2 pCi/cm2) and a significantly lower rate of trabecular bone formation (P < 0.01). The 239Pu concentration at these sites remained nearly constant throughout the experimental period. The degree of the initial deposition of 239Pu on trabecular bone surfaces and the rate of trabecular bone turnover may play a role in the genesis of 239Pu-induced osteosarcomas.