The concentration of sodium, potassium and chloride in rabbit submandibular saliva during postnatal development

Saliva was collected from the cannulated ducts of submandibular glands of rabbits at various ages from birth to adulthood and analysed for sodium, potassium and chloride. Saliva was obtained at all ages by electrical stimulation of the parasympathetic innervation to the gland. On the day of birth (day 1), salivary sodium was 108.5 +/- 3.4 mM (n = 8) and chloride was 89.9 +/- 3.6 mM (n = 9) falling to adult-like concentrations of 5.7 +/- 0.6 mM (n = 13) and 16.5 +/- 1.2 mM (n = 9) respectively by day 10. On Day 1, salivary potassium was 23.9 +/- 1.8 mM (n = 7) and rose progressively to 76.8 +/- 2.5 mM (n = 8) on day 17. Adult potassium concentration was 30-40 mM. A wide range of flows was obtained at all ages and at each age sodium and chloride concentrations were approximately constant at all flows. Therefore the changes in electrolyte concentration cannot be explained by differences in flow. The results suggest a maturation of ductal transport of sodium, potassium and chloride ions concurrent with the structural maturation of striated duct cells.