Circadian rhythms in the concentrations of protein and the main electrolytes in human unstimulated parotid saliva

Abstract

Seven subjects collected left-parotid and extra-left-parotid (i.e. residual whole saliva) simultaneously, under resting conditions, at about five different times each day, for about 12 consecutive days. Least-squares cosine analyses of the data to test for the presence of circadian rhythms demonstrated significant rhythms for the subjects as a group, in the concentrations of protein, sodium, potassium, magnesium, chloride and inorganic phosphate but not calcium in unstimulated parotid saliva, and in the concentrations of sodium, potassium and chloride but not inorganic phosphate in unstimulated residual whole saliva. The circadian rhythms in the concentration of protein in unstimulated and stimulated parotid saliva were not affected by dexamethasone-induced suppression of the normal plasma cortisol rhythm.