Studies on the Calcium-protein Relationship with the Aid of the Ultracentrifuge” Iii. Influence of Augmentation of Serum with Calcium and Phosphate Salts

Since the calcium-protein relationship for a purified protein is adequately described by the law of mass action (l), it follows that the inconsistencies between the total calcium and total protein for sera (2) probably represent the cumulative effect of a number of variables. The present report deals with some of these variables as follows: the effect of excessive amounts of CaClz on the calcium-protein relationship, and the effect of excessive amounts of calcium and phosphorus on the calcium-phosphorus-protein relationship in serum. There is evidence in the literature to show that the addition of excessive amounts of calcium or phosphorus to serum results in the formation of compounds of a colloidal nature whose exact composition is unknown. Such complexes must affect the concentration of ionized calcium and therefore the calcium-protein relationship. The ultracentrifuge and the methods for determining nitrogen and calcium have been described (1). Phosphorus was determined on trichloroacetic acid filtrates by the Fiske and Subbarow method (3) as adapted to the photoelectric co1orimeter.l The pH was adjusted to the original value of the serum (about 7.8) after either N%HPOk or CaClz was added. The pellet that usually formed after the addition of salts was not analyzed, thus representing a loss of protein, calcium, or phosphorus. Calcium and Protein Distribution in Serum after Augmentation with Calcium-varying amounts of CaClz were added to aliquots of stock human and horse serum, respectively. Graphs showing the calcium-protein relationships for the respective sera are presented in Figs. 1 and 2. The results are plotted as broken line graphs, since no linear relationship could be established. The general slope of the lines increases with the increased calcium concentration in a manner noted for calcium-casein solutions (1). The graphs obtained represent the combined effects of at least three