The relation between skeletal and extracellular-fluid magnesium in vitro.

1. Femora from control and magnesium-deficient rats were incubated in media of different magnesium concentrations. 2. Magnesium was lost at the same rate from fresh and boiled bones to a magnesium-free medium. 3. The equilibrium established was dependent on the magnesium concentrations in both the bone and the medium. 4. Parathyroid extract increased the rate of magnesium loss from bone to a magnesium-low medium containing bovine serum (50%), but had no effect in a protein-free medium.