Suppression of mucus secretion in the ciliated epithelium of frog palatine mucosa by perfusion with electrolyte solution.

We investigate the effects of perfusion with electrolyte solution on secretion of mucus by the frog palatine mucosa. The amount of mucus secreted was determined by measuring the contents of hexosamine in the mucus. Ciliary movement was examined by the particle transport method. The goblet cells, which secret mucus in the ciliated epithelium, were examined under light and electron microscopes after the perfusion with Ringer's solution. While the mucus secretion was almost completely suppressed by the perfusion with Ringer's solution, the ciliary movement was not suppressed. This suppression was also observed in the presence of bromhexine, pilocarpine or adrenaline, drugs which enhance mucus secretion. Acceleration of ciliary movement as induced by acetylcholine, adrenaline, and serotonin was potentiated by perfusion with Ringer's solution. The mucus secretion was not suppressed by perfusion with A Tris-HCl-substituted Ringer's solution lacking Na+ and was partially suppressed when perfused with a Tris-Cl-substituted Ringer's solution free of Ca2+. Following perfusion with Ringer's solution, many granules containing mucus were observed in the lower part of a goblet cell in the ciliated epithelium. Moreover, shrinkage of the goblet cell but not the ciliated cell was observed electron-microscopically. The difference in membrane permeabilities to Na+ and Ca2+ between the ciliated cell and the goblet cell may play a role in the suppression of mucus by the palatine mucosa.