Autoradiographic comparison of 96Tc-pyrophosphate and 45Ca bone uptake

To compare the skeletal distribution of calcium and pyrophosphate complexes, autoradiograms of the growing zone of 10-week-old rabbit femurs were performed. Due to its stability to chemical and enzymatic hydrolysis and to the relatively long half-life of the isotope, 96Tc-labelled pyrophosphate was used. Calcium uptake was studied with carrier free 45Ca. For both tracers, the blood supply plays a significant role by delivering the radiopharmaceuticals. In a second step their partition was governed by mixing in different bone structures: calcium was incorporated inside the bone trabeculae and the mineral mass whereas labelled pyrophosphate remained in linear patterns surrounding bone spicules.