Dark-staining bodies in the conjunctival epithelium of rats after multiple topical challenges with compound 48/80

Over a 17-day period, 96 Sprague-Dawley rats received approximately daily topical applications of compound 48/80 to the ocular surface of one eye and phosphate-buffered saline (PBS) to the other eye. On histologic examination, dark-staining bodies appeared in the conjunctival epithelium in all 48/80-challenged eyes after day 3. These epithelial dark bodies (EDBs) rarely appeared in PBS-challenged or in single-dose 48/80-challenged tissues. The EDBs, between two and 15 per 30 fields at x 1000 under light microscopy, were limited to the conjunctiva near the fornix rather than near or over the tarsal plate. We hypothesize that these EDBs are associated with repeated application of secretagogue to the conjunctiva.