ACTION OF OUABAIN ON SUBMAXILLARY SECRETION IN THE DOG

¹ Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad de El Salvador, San Salvador, El Salvador

Flow rate, Na⁺, K⁺, Cl^-, and total osmolyte concentrations in pilocarpine-stimulated submaxillary glands of dogs perfused in retrograde fashion with isotonic saline were studied after ouabain. 1) Intraluminal injection of 0.5 ml of solutions containing ouabain decreased the flow rate and increased both Na⁺ and K⁺ concentrations of stimulated secretion when used in concentrations of 10^-4 and 10^-3 M. Ouabain, 10^-5 M, decreased the flow rate less markedly and did not affect electrolyte concentrations significantly. Ouabain, 10^-6 M, similarly decreased the flow rate and decreased both Na⁺ and K⁺ concentrations. 2) Arterial injections of 0.5 ml of 10^-3 M ouabain did not change the flow rate but increased Na⁺ and K⁺ concentrations of submaxillary secretion. Ouabain, 10^-4 M, increased Na⁺ slightly and did not affect K⁺. 3) Constant arterial infusions of 3.498 ml of 10^-3 M ouabain completely abolished the flow of saliva. Similar infusions of 10^-4 M ouabain decreased flow rate and increased Na⁺ slightly. Ouabain 10^-5 and 10^-6 M, produced a similar decrease in flow rate and tended to decrease both Na⁺ and K⁺ concentrations. 4) The glycoside did not affect Cl^- concentration or osmolality from either side of the gland epithelium. It is concluded that ouabain has a biphasic effect on Na⁺ and K⁺ transport in dog submaxillary gland and that the observed effects on the luminal and contraluminal surfaces could be explained on the basis of two separate mechanisms or "pumps," a relatively inaccessible acinar mechanism and a more readily reached ductal pump. The possibiity that some of these mechanisms or pumps are located at the mucosal surface of the epithelium is discussed.