Salivary electrolyte concentrations and electrical potential difference across the parotid salivary duct of anaesthetized sodium-replete sheep.

Salivary flow rate and the concentrations of electrolytes in parotid saliva and arterial plasma from anaesthetized sodium-replete sheep were measured before, during and after ipsilateral intracaroitd infusion of acetylcholine at 10 nmol min-1 to ascertain whether anaesthesia altered the relation between salivary flow and sodium concentration. The potential difference (PD) between the lumen of the parotid duct and the vascular system was also measured. Concentrations of salivary sodium and phosphate were decreased and potassium concentration and total CO2 content were increased when rate of salivary flow was increased by acetylcholine infusion. Salivary chloride concentration was reduced in five experiments and increased in three experiments when flow rate was elevated. Thus the flow-composition relations of parotid saliva from anaesthetized sheep were essentially the same as those for saliva from conscious animals. The PD between the lumen of the parotid duct and blood at resting flow rates was 9.4 +/- 1.07 mV, lumen negative. At high flow rates, stimulated by acetylcholine infusion, the PD increased to 21.9 +/- 2.20 mV, lumen negative. This increase in PD of the duct epithelium appeared to depend on changes in the composition of saliva arriving at the site of potential measurement.