[Quantitative assessment of metabolic bone disease in rat models by dual tracer method]

The usefulness of radionuclide techniques for early differential diagnosis of metabolic bone disease has been controversial. We tried to develop a new method to distinguish alterations in bone metabolism prior to radiologic changes, measuring 24-hr whole-body retention (WBR) and femoral uptake of two radiopharmaceuticals (47Ca-chloride, 99mTc-MDP). Control normal (C), osteoporosis (P) osteomalacia (M) and steroid-induced osteoporosis (S) were produced in 60 eight-week old Wistar male rats by means of dietary manipulation and steroid administration. Fine detail radiographs of the femurs and bone specimens were obtained over six weeks at two week intervals. Good correlation between WBR and femoral uptake of 47Ca was noted (r = 0.86, p less than 0.01). WBR ratios of 47Ca were significantly higher in the M and S groups and were lower in the P group when compared to the C group throughout the study. WBR ratios of 99mTc-MDP were significantly higher in the M group and were lower in the S group from the 2nd week. Fine detail radiographs analysis by microdensitometry revealed significant osteopenia in the S, M and P groups from the 4th week. The dual tracer method was found to distinguish alterations in bone metabolism in the groups examined prior to detectable radiologic changes.