The skeletal deposition of yttrium.

As part of a program devoted to studying the accumulation of metallic ions by mammalian skeletal tissue, it was decided to investigate the uptake of yttrium by rats. Although this element is encountered but rarely in biochemical investigations, its behavior in the body has become important since its discovery as one of the major products of nuclear fission (1). Radioactive isotopes of yttrium have been reported to be removed rapidly from the blood and deposited in bone, where the element remains for very long periods of time (2, 3). The same general behavior has been noted for radioisotopes of the alkaline earth elements and for members of the lanthanide and actinide rare earth series. However, on the basis of radioautographs, two fundamentally different modes of bone deposition have been reported. Srgo seems to be deposited more or less uniformly throughout cortical bone, in close association with bone salt. Yttrium, on the other hand, appears to be laid down in the osteoid matrix (4, 5). By providing Sr in the drinking water, a level of as high as 5 per cent Sr in the bone ash can be attained with mice (6). In view ‘of these observations, it, seemed desirable to learn whether or not yttrium and, by inference perhaps, the lanthanide elements are as avid “bone seekers” as strontium has proved to be. Radioactive yttrium was not applied in the present experiments, in order to avoid possible disturbance of normal osteoblast and osteoclast cellular activity by irradiation.