Effects of hypertonic solutions on conjunctival epithelium and mucinlike glycoprotein discharge

A simple, semiquantitative, histochemical method using periodic acid-Schiff (PAS) staining was developed to measure the mucinlike glycoprotein content of bathing solutions exposed to rabbit conjunctiva. Rabbit eyes were bathed in vivo in solutions of various tonicity (160, 260, 300, 330, and 363 mOsm/L). Eyes bathed in hypotonic or isotonic solutions (160, 260, and 300 mOsm/L) exhibited a steady-state glycoprotein secretion (50-100 μg/h). In hypertonic solutions (330 and 363 mOsm/L), glycoprotein discharge increased to 150-360 μg/h when the solutions were exchanged hourly for 6 h, but glycoprotein discharge increased to a much lower rate (100-167 μg/h) after prolonged bathing for 6 h without solution exchange. Periodic acid-Schiff-positive glycoprotein aggregates were noted more frequently on the filters of hypertension solutions than on those of other tonicity. After eyes were bathed in hypertonic solutions, increased disruption of the surface epithelium, increased abnormal discharge of mucin granules, and decreased goblet cell density were noted in the biopsied conjunctiva. These data suggest that mucinlike glycoprotein secretion from the conjunctival goblet cells can be enhanced by the tonicity of the bathing solution, and that nonphysiological hypertonic solutions can also affect the conjunctival epithelium.