Effect of angiotensin II on parotid saliva secretion in conscious sheep

Intravenous infusion of angiotensin II over the dose range 3-20 microgram/h for 15 min caused a dose-dependent reduction in parotid saliva secretion and increase in arterial blood pressure in conscious sheep. The blood levels of angiotensin II contrived by these infusions were probably within the physiological range for sheep. Infusion of angiotensin II (3 microgram/h) into the carotid artery ipsilateral to the parotid gland under study caused greater reduction in saliva secretion rate than an equivalent infusion of angiotensin II into the contralateral carotid artery. This result suggests a direct effect of angiotensin II at the parotid, possibly by a constrictor action on its vasculature or by altering water and electrolyte transport by the gland. In sodium-deplete sheep, intravenous infusion of the angiotensin antagonist saralasin (1 mg/h for 1 h) caused transient increase of saliva flow for 20-30 min. It is suggested that angiotensin II may have a physiological role in regulating parotid saliva secretion during sodium depletion.