A method for determining concentrations of calcium complexes in human parotid saliva by gel filtration

Saliva was collected at two flow rates (approx. 0.15 ml/min, pH 6.6 and 1.5 ml/min, pH 7.4) from one subject. The saliva was gel-filtrated at 37 °C in a column, equilibrated and eluted with a buffer containing Ca²⁺ at a concentration equal to that of saliva. Three peaks containing the Ca complexes were identified as proteins (I), phosphate, citrate, lactate (II) and bicarbonate (III). In the weakly stimulated saliva, the total Ca was 0.61 mmol/l, distributed as Ca²⁺ (45 per cent), bound to proteins (10 per cent), complexes to the inorganic ions (35 per cent) and to the organic acids (10 per cent). For strongly stimulated saliva (total Ca 1.15 mmol/l), the corresponding figures were 43.5, 8.7, 40 and 7.8 per cent respectively. The higher total Ca concentration in the strongly stimulated saliva was recovered mainly as Ca²⁺ and Ca complexed to carbonate.