The comparative in vitro release of calcium from dried and defatted eel and rat bone fragments, and its possible significance to calcium homeostasis in teleosts

Abstract

The in vitro release of calcium from dried and defatted fragments of eel bone and rat bone was examined in a number of inorganic solvents and in eel and rat plasma. In each inorganic solvent, the rate of withdrawal of calcium from eel bone exceeded the rate of withdrawal from rat bone; and at equilibrium, the eel bone supported a higher solvent-calcium concentration than did the rat bone. In eel plasma, fragments of eel bone supported a plasma calcium concentration greater than the concentration of calcium in normal plasma in vivo. These results are consistent with the view that in normal eels, the plasma is undersaturated with calcium with respect to the simple solubility of bone calcium.The hypothesis that the simple solubility of bone calcium plays a greater role in the maintenance of calcium homeostasis in fishes than it does in mammals is discussed in relation to the observations made.