Calcium Metabolism of Bone in Vitro. Influence of Bone Cellular Metabolism and Parathyroid Hormone*

metabolic activity of cells; second, to examine more directly which steps in the metabolic sequence and which metabolites of cells might be associated with mobilization of mineral from bone; and finally, to explore the effects prior treatment of the animals with parathyroid hormone might have on these phenomena. The results of these experiments indicate that 18 per cent of the Ca concentration maintained by normal living bones in their surrounding media was related to metabolic phenomena; about onehalf of this being associated with glucose metabolism. No direct correlation, however, could be found between rates of lactate production (previously shown to be the chief end-product of glucose metabolism in this tissue) and Ca concentration. Parathyroid hormone treatment increased the total concentration of calcium 17 per cent above normal controls. The mechanism of this action appeared to involve both an increase in the passive solubility of the bone mineral and changes in the pattern of cellular metabolic effects. No effects on total P concentrations were observed in any of the experiments with surviving bone samples.