In the dispersed acinar cells of the submucosal nasal gland in the guinea pig, intracellular Na+ concentration ([Na+]i) was measured with a microfluorimetric imaging method and the cytosolic indicator dye, sodium-binding benzofuran isophthalate, under HCO3(-)-free conditions. In the unstimulated condition, the [Na+]i was averaged to 12.8 +/- 5.2 mM. Addition of 100 microM ouabain or removal of external K+ caused an increase in [Na+]i. Replacement of external Cl- with NO3- or addition of 0.5 mM furosemide reversibly decreased the [Na+]i. The recovery process from the reduced [Na+]i was inhibited by removal of either K+ or Cl- in the bath solution. These findings indicate the presence of a continuous influx of Na+ coupled with K+ and Cl- movement. Application of acetylcholine (ACh, 1 microM) caused an increase in [Na+]i by about 15-20 mM, which was completely inhibited by addition of 10 microM atropine. Increased cytosolic Na+ induced by ACh was extruded by the Na(+)-K+ pump. Removal of external Cl- and addition of 50 microM dimethylamiloride inhibited ACh-induced increase in [Na+]i by about 66% and 19%, respectively. In both unstimulated and stimulated state, Na(+)-K+ pump, Na-K-Cl cotransport, and Na(+)-H+ exchange play a critical role in maintaining intracellular electrolyte environment and in controlling a continuous secretion of nasal fluids.
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