Abstract
Summary
The curve describing the uptake of 45Ca by bone powder or by synthetic hydroxyapatite shows an initial rapid fall in radioactivity of solution followed by a mono-exponential decline at a slower rate. Wash-out experiments were performed on the labelled crystals before and during the period of mono-exponential fall by resuspending the crystals, collected by filtration, in medium free of isotope. More than 80% of radiocalcium could be removed from the crystal phase by this procedure regardless of the period of labelling. Results from published reports are interpreted to show that “back-diffusion” of isotope from bone into solution is operative only at a certain region of the uptake curve; our studies contradict this interpretation.
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