The uptake of sodium-22 by bone and certain soft tissues

Groups of young rats were intravenously injected with²²Na. At various short time intervals thereafter samples of liver, skeletal muscle, kidney, serum and thoroughly-cleaned compact bone were removed and assayed for both stable and radioisotopic concentrations of sodium. Penetration of²²Na into the analysed soft tissues was very rapid and after 10 minutes only a small amount of tissue sodium remained relatively unavailable to the circulation. The rate of²²Na-uptake by the tibial compact bone could be divided into two components:

1. a fast process which appears to be limited only by the blood circulation in bone and is compatible with the cycling concept and
2. a much slower process which may involve solid state diffusion, recrystallisation and physiological remodelling and which is adequately defined by a power function expression.