Use of 85Sr as an indicator of bone mineral replacement in dogs after disuse demineralization

The left front legs of two beagle dogs were immobilized for 2 months; the right front legs of each were used as weight-bearing controls. Bone mineral replacement after immobilization was studied by giving intravenous injections of 85Sr (Strontium-85). After allowing the radioisotope to disappear from the soft tissues, measurements were made on only that remaining in the bone. The 85Sr uptake in the bone of the leg which had been immobilized was up to 400 percent higher than that in the control leg. This increased 85Sr uptake probably resulted from only a few percent loss in bone mineral during immobilization and suggests that losses of less than 1 percent can be detected and located. The sensitivity, simplicity and mineral radiation dose associated with this technique indicates potential application for use in human bed-rest and space-flight studies