Measurement of extra-cellular fluid change in salivary gland using an impedance method

The method of electrical impedance measurement was tested for its usefulness in monitoring of extra-cellular fluid (ECF) in the dog submandibular gland during salivary secretion. Measurements were performed during rest and stimulated state with or without blood supply. During stimulation with blood supply, the conductivities of the gland decreased to some extent. During stimulation without blood supply, the decrease in conductivities was markedly enhanced. The decrease of ECF compartment during stimulation without blood supply was ascertained by the stereological measurement. Coincidence of conductivity decrease and histologically observed decrease of ECF compartment supports the usefulness of impedance measurement for monitoring of ECF during secretory activity of gland tissue. The present study also shows that the interlobular space decreased mainly during stimulation when blood supply is absent. This indicates that, among ECF space, the interlobular space plays an important role as a fluid reservoir in the salivary gland.