EFFECTS OF FLOW RATE AND DURATION OF STIMULATION ON CONCENTRATIONS OF PROTEIN AND MAIN ELECTROLYTES IN HUMAN PAROTID SALIVA

The concentrations of protein and of many of the main electrolytes in human parotid saliva from 10 subjects were found to be strongly influenced by duration of stimulation as well as by flow rate. When flow rate was maintained constant for 15 min at 0.25,0.50 or 1.00 ml/min, the concentrations of sodium, potassium, magnesium and pCO2 achieved constant values within the first 1 or 2 min of stimulation and thereafter were independent of time. However, the pH and the concentrations of bicarbonate, chloride, mono and dihydrogen orthophosphate, calcium and protein varied with time throughout the 15 min of stimulation. Protein concentration fell at the beginning of stimulation but increased with duration of stimulation, particularly at the highest flow rate. Bicarbonate concentration increased progressively with time whilst chloride concentration showed a reciprocal decrease. The degree to which chloride was replaced by bicarbonate in the salivary ducts was low initially but increased throughout the 15 min of stimulation at constant flow rate. The time-dependence of this exchange accounts for the influence of duration of stimulation on the pH and the concentrations of mono and dihydrogen orthophosphate but cannot account for the time-dependent changes in protein and calcium secretion. The pCO2 in stimulated saliva was in the arterio-venous range of plasma. © 1969.