EFFECT OF AGE ON RADIOSODIUM EXCHANGE IN BONE (RAT)

On a wet weight basis, bone from young animals contains more water and chloride, and less sodium and calcium than that of the adult. In the young anlmal, a much larger fraction of the skeletal sodfum exchanges readily with radiosodium. However, since the skeleton of the older animal has a much higher sodium concentration, the total amount of sodium per unit skeletal weight which is available for exchange does not vary appreciably with age. Sodium in bone is considered metabolically to consist of three phases: fluid phase sodium, represented by that contained in the chloride space; the exchangeable portion of the crystal phase Na; and the nonexchangeable Na of the crystal phase. Changes in the magnitude of each of these phases occurs during growth in the rat. (auth)