Secretion and transductal fluxes of ions in exocrine glands of the mouse

The secretory mechanisms and transductal fluxes of water and monovalent ions were investigated in the parotid, submaxillary, and pancreas of the Swiss Webster mouse by using micropuncture, microperfusion, and microanalytical techniques. The osmolarity and the concentrations of monovalent ions of the fluid obtained from the intercalated ducts of the salivary glands during stimulation with pilocarpine were similar to or slightly higher than those observed in the mouse plasma, and they did not change with changes in the flow rate. Salivary hypotonicity was produced by net efflux of Na and Cl in excess of water in the intralobular ducts of the glands while net transductal influx of small amounts of K took place. These transductal events resulted in the observed, flow rate dependent changes in the composition of the respective salivas. In the pilocarpine or secretin stimulated mouse pancreas, the acinar fluid was isotonic or slightly hypertonic to plasma with high Cl and low HCO₃ concentrations as in the rat pancreas. During both forms of secretory stimulation, no net transductal fluxes of anions took place, and the ionic composition of the final pancreatic juice was identical to that of the primary secretory (acinar) fluid. By using simultaneous measurements of amylase concentrations in the primary fluid and final product of parotid and pancreas and by in situ microperfusion of the main submaxillary duct, it was demonstrated that the duct systems of these glands are impermeable to water. The present experiments suggest that in these three exocrine glands of the mouse, the secretory process appears to be active transacinar transport of electrolytes.