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

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 HCO₃^–. 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.