Characteristics of parotid saliva from the common wombat ( Vombatus ursinus )

Saliva was collected from the parotid glands of anaesthetized common wombats ( Vombatus ursinus ) to ascertain the maximal flow rates, salivary composition and possible adaptations to the diet. After temporary catheterization of the parotid duct through the oral opening, salivary secretion was evoked by ipsilateral intracarotid infusion of acetylcholine at varying rates to produce salivary flow rates ranging from 0.017±0.0012 ml.min ‐1 (0.62±0.037 μmin ‐1 .kg ‐1 body weight) to 2.00±0.148 ml.min ‐1 (70.5±3.21 μl.min ‐1 kg ‐1 body weight). The concentrations of Na (22.2±5.50 to 107.0±5.2 mmol.1 ‐1 ) and H+ (12.5±1.73 to 17.4±1.40 nmol‐1 ‐1 ) were positively correlated with salivary flow rate. The concentrations of K (99.3 ± 6.51 to 13.7±0.62 mmol.1 ‐1 ), Ca (1.36±0.229 to 0.74±0.021 mmol.1 ‐1 ), Mg (1.14±0.092 to 0.03±0.002 mmol.1 ‐1 ), HCO 3 (65.3±2.43 to 55.7±1.70 mmol.1 ‐1 ), PO 4 (3.30±0.334 to 0.51±0.038 mmol‐1 ‐1 ), protein (2.08±0.284 to 0.49±0.084 g.1 ‐ ), amylase activity (6.75±1.515 to 1.97±0.538 mkat.1 ‐1 ) and urea (10.9±0.89 to 3.88±0.28 mmol‐1 ‐1 ) were negatively correlated with flow rate. The relationships between salivary flow and C1 concentration or osmolality were diphasic: negative at low flows and positive at high flow rates. The patterns of excretion of the major anions in the saliva differed substantially from those reported for parotid glands of other marsupials. The saliva had levels of amylase activity which were far higher than those of other marsupials and which may be an adaptation to a diet rich in carbohydrate. Salivary Na/K ratios were not decreased by high‐rate intracarotid infusion of aldosterone (80–100 μg.h ‐1 for 4 h) which indicated that the wombat gland, like the parotid glands of macropods, requires chronic exposoure to high levels of mineralocorticoides to sensitize the gland.