Micropuncture and cannulation study of water and electrolyte excretion in the isotonic-secreting cat sublingual salivary gland

Summary The electrolyte composition of saliva from the isotonic-secreting cat sublingual gland has been compared with that of samples of acinar secretion obtained by micropuncture. The electrolyte concentrations in the acinar fluid, which were not affected by parasympathomimetic stimulation, resembled those of the primary fluid of hypotonic-secreting glands; they were [Na]=141 mM±5 S.E.M.; [K]=9.1±1.5 mM; [Cl]=128±4 mM.Following stimulation with carbachol, Na and K concentrations in final saliva showed, in contrast to saliva from hypotonic-secreting glands, only a slight flow dependence and Na concentrations were never lower, nor K concentrations higher than their respective concentrations in acinar fluid. Cl concentrations, on the other hand, were always greater than in primary fluid, ranging from 136±3 mM at low secretory rates to 162±6 mM at highest secretory rates.It was concluded that cat sublingual saliva is formed in 2 stages. First, an acinar secretion of approximately plasma-like electrolyte composition is formed by processes which seem essentially similar to those of all other exocrine glands so far studied by micropuncture. Second, the saliva is modified during passage along the gland excurrent duct system by secretion of Cl in exchange for HCO₃. The duct system is atypical of salivary glands but seems to resemble that of the pancreas in lacking transport mechanisms for Na and K.A preliminary account of this study has been reported to a meeting of the Australian Physiological and Pharmacological Society held at the University of Adelaide in May 1972 [12]. The project was supported by the National Health and Medical Research Council of Australia.Mr. Kaladelfos held a B.Sc. (med.) studentship from the National Health and Medical Research Council of Australia in 1970–1971 and a Summer Vacation Studentship from the National Heart Foundation of Australia in 1971–1972.