Inhibition of sodium transport by angiotensin II in the main duct of the rabbit mandibular gland isolated and perfused in vitro

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Abstract
Summary The effect of angiotensin II on nett electrolyte transport by the main duct of the rabbit mandibular gland was investigated in vitro using a perfused duct preparation bathed in a Haemaccel®-nutrient salt solution. In a bath concentration of 4×10−10 M, angiotensin reduced nett absorption of Na+ and Cl− by about 8% and depolarized the transepithelial electrical potential difference (P.D.) by about 13%; the drug had no effect on ductal transport of K+ and HCO −3 . In both lower (4×10−11 M) and higher (4×10−9 M) concentrations, angiotensin had qualitatively similar effects. After exposure to the hormone for about 30 min, Na+ transport and P.D. became unstable and gradually fell away towards zero. It is concluded that angiotensin in physiological concentrations has a specific inhibitory effect on Na+ absorption by salivary duct cells which could arise either from a change in the Na+ pump rate or from a conductance change in the apical or basal membrane of the epithelial cell.