Electrolyte composition of parotid saliva from sodium-replete red kangaroos (Macropus rufus)

Abstract

Saliva was collected from the parotid salivary gland of anaesthetized sodium-replete red kangaroos (Macropus rufus) by catheterization of the parotid duct through its opening in the mouth. Salivary secretion was stimulated by ipsilateral intracarotid infusion of acetylcholine at varying rates to produce salivary flow rates ranging from 0.056 +/− 0.0042 (S.E. of mean) to 4.509 +/− 0.1136 ml min-1. The concentrations of sodium (142.2 +/− 1.93 to 157.0 +/− 1.17 mmol l-1), calcium (40.1 +/− 7.08 to 72.8 +/− 8.0 mumol l-1) and bicarbonate (68.6 +/− 3.48 to 143.3 +/− 0.67 mmol l-1) and the osmolality (270.1 +/− 2.98 to 291.7 +/− 2.10 mosmol kg-1) were positively correlated with salivary flow rate, whereas the concentrations of potassium (11.4 +/− 0.57 to 6.92 +/− 0.19 mmol l-1), magnesium (206.0 +/− 34.1 to 9.3 +/− 0.78 mumol l-1), hydrogen ion (17.0 +/− 1.89 to 6.82 +/− 0.49 nmol l-1), chloride (30.7 +/− 2.41 to 4.11 +/− 0.23 mmol l-1) and phosphate (47.6 +/− 2.65 to 14.9 +/− 0.81 mmol l-1) were negatively correlated with flow rate. The relationships between flow rate and concentration were curvilinear for all the inorganic solutes. The rates of secretion for each ion and for total solute were positively correlated with salivary flow rate. These regressions for sodium, potassium, calcium, hydrogen ion, bicarbonate and osmolality were always linear, with highly significant correlation coefficients and variance ratios, which indicated that the changes in concentration of these ions were related solely to flow rate and were not due to any other factor modifying glandular function. Spontaneous secretion was not observed during anaesthesia.