Stop-flow effects on human salivary composition and hydrostatic pressures

Abstract

Saliva was collected, after cannulation of the parotid duct of six subjects, either without stimulation or at a constant flow-rate (FR) using gustatory stimulation. The normal secretory pressure at different parotid saliva FRs, the pressure developed during stop-flow (SF) and the compositional changes induced by SF were determined. Gustatory stimulation, where employed, was continued at the same intensity whilst flow was stopped and the pressure measured with a strain gauge. On SF, there was a rapid initial pressure increase of 5–20 mmHg, dependent on the preceding FR, which is interpreted as the normal secretory pressure, followed by a more gradual increase to a mean of 45 mmHg at high intensities of continued gustatory stimulation but with oscillations in amplitude of about 20 mmHg. Following SF for 3 min at a preceding FR of 1 ml/min, total protein concentration was temporarily decreased by about 40 per cent but several-fold increases in the concentrations of Mg, glucose and albumin occurred. Thus, following SF there may be a transient increase in permeability of the salivary tubules which allows some equilibration between the components of extracellular fluid and saliva.