Subject(s)
Angiotensin II/pharmacology , Carotid Arteries/drug effects , Hydrostatic Pressure , Inulin/metabolism , Ouabain/pharmacology , Pressure , Animals , Autoanalysis , Electrolytes/metabolism , Neurotransmitter Agents/pharmacology , Perfusion , Potassium/metabolism , Sodium/metabolism , Swine , Valine/pharmacologyABSTRACT
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 X 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 X 10(-11) M) and higher (4 X 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.
Subject(s)
Angiotensin II/pharmacology , Sodium/metabolism , Submandibular Gland/metabolism , Animals , Biological Transport, Active/drug effects , Epithelial Cells , Epithelium/metabolism , Male , RabbitsABSTRACT
1. Angiotensin has previously been shown to inhibit distal renal tubular sodium reabsorption. As a consequence of this, or independently, it might influence the distal handling of other electrolytes. We have therefore examined the effects of angiotensin on the distal reabsorption or secretion of a spectrum of electrolytes. 2. Standard bilateral stop-flow studies were done on anaesthetized, adrenalectomized rabbits, in which the effects of intravenous infusions of either 0-02-0-05 mug min-1 kg-1 or 1 mug min-1 kg-1 of angiotensin were compared with control stop-flow results. 3. The lower dose of angiotensin inhibited distal sodium, chloride, water and magnesium reabsorption, inhibited distal hydrogen secretion and stimulated distal potassium secretion. The higher dose of angiotensin produced these changes and additionally inhibited distal calcium reabsorption. Most of the observed changes were dose-related. The low dose of angiotensin did not significantly raise blood pressure but the high dose was pressor. 4. Changes in the stop-flow patterns induced by the higher dose of angiotensin were compatible with, and may help to explain, the changes it produced in urinary excretion of sodium, chloride, potassium, magnesium and calcium in clearance studies before stop-flow. Suppression of hydrogen secretion caused by both doses of angiotensin in the stop-flow studies was also reflected by reductions in acid excretion produced by these infusion rates in additional experiments performed by clearance methods in acid-loaded, conscious rabbits. 5. The results support the view that angiotensin may have an important intrarenal role, at least in rabbits.
