SECRETION OF ELECTROLYTES, PROTEIN AND UREA BY THE MANDIBULAR GLAND OF THE COMMON WOMBAT (VOMBATUS-URSINUS)

Saliva was collected from the mandibular glands of anaesthetized commo n wombats (Vombatus ursinus) to ascertain maximal flow rates, salivary composition and possible adaptations, particularly PO43- secretion, t o assist digestion. After temporary catheterization of the main duct t hrough its oral opening, salivary secretion was evoked at flow rates r anging from 0.02+/-0.002 (+/-SEM) ml . min(-1) (0.7+/-0.07 mu l . min( -1). kg body weight(-1)) to 0.4+/-0.05 ml . min(-1) (14+/-1.9 mu l . m in(-1). kg body weight(-1)) by ipsilateral intracarotid infusion of ac etylcholine. The [Na+] (15+/-5.1 to 58+/-8.6 mmol . l(-1)) and [HCO3-] (35+/-1.9 to 60+/-1.9 mmol . l(-1)) were positively correlated with s alivary flow rate. The [K+] (58+/-5.2 to 30+/-2.4 mmol . l(-1)), [Ca2] (10.4+/-1.67 to 4.1+/-0.44 mmol . l(-1)), [Mg2+] (0.94+/-0.137 to 0. 17+/-0.032 mmol . l(-1)), [Cl-] (71+/-9.2 to 45+/-6.0 mmol . l(-1)), [ urea] (9.3+/-0.79 to 5.1+/-0.54 mmol . l(-1)), H+ activity (29+/-1.6 t o 17+/-1.6 nEq . l(-1)) and amylase activity (251+/-57.4 to 92+/-23.3 mu kat . l(-1)) were negatively correlated with now. Both concentratio n and osmolality fell with increasing flow at the lower end of the flo w range but osmolality always increased again by maximal flow whereas the relation between protein and flow was not consistent at the higher levels of flow and stimulation. Salivary [PO43+] was not correlated w ith flow and at 3-14% of the plasma concentration was extremely low. T hus, in contrast to its nearest relative, the koala (Phascolarctos cin ereus), the wombat secretes little PO43+ presumably because it does no t need high levels of PO43+ is its saliva to facilitate microbial dige stion of plant fibre.