Submandibular secretion in the dog after intraluminal injections of amiloride

The effects of amiloride on flow rate, osmolarity, Na⁺, K⁺ and Cl^? concentrations were studied in the submandibular glands of dogs. The drug was injected in a retrograde fashion into the duct system of the gland, which was subsequently stimulated to secrete with pilocarpine. In concentrations of 10^?4 and 10^?3 M, amiloride increased the Na⁺ concentration but did not significantly alter the K⁺ concentration of saliva. A slight decrease in Cl^? concentration was observed at high flow rates after 10^?4 M amiloride, but otherwise the drug did not significantly affect the Cl^? concentration of stimulated salivary secretion. The diuretic has a measurable mucosal (luminal) effect on Na⁺ transport in dog submandibular gland, which is similar to that reported in amphibian epithelia. Its lack of effect on K⁺ excretion differs from findings reported in other epithelial structures, where it has a marked K⁺-sparing effect. The drug increased the salivary osmolarity in a fashion similar to Na⁺, a finding that suggests a dissociation between Na⁺ and water transport in salivary duct epithelium.