The effects of exercise on protein and electrolyte secretion in parotid saliva

1. Ten subjects collected ten 1 min samples of parotid saliva at a constant flow rate 1-2 hr before exercise, immediately after running 3-8 miles and 3 hr after exercise. 2. Exercise had no significant effects on the concentration of sodium, potassium, calcium, magnesium, chloride, bicarbonate or inorganic phosphate. 3. Exercise caused a marked elevation in total protein concentration and in seven of the subjects the initial samples after exercise were cloudy due to protein precipitation. The precipitated protein could be dissolved in sodium EDTA. 4. The saliva samples collected immediately after exercise from the seven subjects in which precipitation occurred contained higher concentrations of protein, calcium and phosphate than in those of the other three subjects. 5. Electrophoretic analysis revealed that all proteins appeared to show a proportional increase in the cloudy saliva, as compared with the clear saliva but differential precipitation of certain proteins occurred in the former which was largely restricted to proteins having a high affinity for calcium phosphate. 6. Electronmicroscopic examination of centrifuged cloudy saliva produced after exercise revealed the presence of rounded droplets of homogeneous structure in contrast to the fine granular deposits produced in clear parotid saliva by in vitro procedures causing precipitation of calcium phosphate crystals on which protein adsorbed.