Binding of calcium by human plasma proteins under simulated physiologic conditions

¹ Department of Biochemistry, Northwestern University Medical School, Chicago, Illinois

The binding of calcium to human plasma albumin, alpha, beta, and gamma globulins was studied with the aid of an ultracentrifuge. The amount of calcium bound to these separated proteins was determined in solutions with electrolyte concentrations and pH within physiological ranges. The total calcium concentration was 2.35–2.90 mm/liter H₂O and the total protein concentration was 3.91–4.29 g/100 ml H₂O. In these solutions no significant differences were found for the binding of calcium (expressed as mm Ca⁺⁺ bound per gram protein) by albumin, alpha, and beta globulins; the average values obtained were, respectively, 0.016, 0.018, and 0.023. Significantly less calcium was bound by gamma globulin; 0.009 mm/gram. The pH was varied between 7.200–7.550 and the sodium chloride concentration between 114–157 mEq Na per liter. These changes did not measurably affect the amount of calcium bound to albumin.

Submitted on July 2, 1963