[Changes in Po2, Pco2, pH, and HCO3 concentration and flow rates in human parotid saliva by tongue sour stimulation at various intervals].

The PO2, PCO2, pH, and HCO3- concentration and flow rates of parotid saliva were observed by tongue stimulation with 3% tartaric acid at various intervals in a human subject after about a one hour rest. The PO2, PCO2, pH, and HCO3- concentrations in parotid saliva were measured with a Blood Gas Analyzer System. The results are summarized as follows: 1) The mean PO2 and PCO2 of parotid saliva immediately before tongue stimulation were about 40 mmHg (range 33-44 mmHg) and 45 mmHg (41-48). There values were similar to those of venous blood. 2) PO2 increased to about 50 mmHg (46-54) 5 to 10 sec. after stimulation, and then 3 to 8 min. later, it decreased to a minimum value of about 28 mmHg (26-29) before returning to the resting level 15 min. after stimulation, when the intervals between stimulations were longer than 2 min., similar changes in PO2 were observed, whereas stimulations every 30 sec. or 1 min. had no effect on PO2. 3) PCO2 increased to about 98 mmHg (85-120) from the resting level of 45 mmHg (41-48) 5 to 10 sec. after stimulation, and returned to the resting level 1 min. after stimulation. When the intervals between stimulations were shorter than 20 min., the peak value of PCO2 by the first stimulation was higher than those induced by the following stimulations. When the interval was 30 sec. or 1 min., only the peak after the first stimulation was observed. 4) The pH of parotid saliva was about 7.4 (7.35-7.5) 30 to 50 sec. after stimulation, and it decreased below 6.5 about 12 min. after stimulation. When the interval between stimulations was 5 min., the pH of the parotid saliva after stimulation was always above 6.5. When the interval between stimulations was 1 min. or 30 sec., it remained at about 7.5. 5) The HCO3- concentration in parotid saliva depends almost exclusively on the pH when Pco2 remained unchanged. When Pco2 was high, however, the HCO3- concentration was affected by the change in Pco2. 6) There was no relationship between changes in the flow rate of parotid saliva and Po2, Pco2, pH, and the HCO3- concentration. Particularly, when the interval between stimulations was shorter than 5 min., the changes in flow rate had no effect on Po2, Pco2, pH, and the HCO3- concentration.