Degranulation of ocular mast cells in rats undergoing systemic anaphylaxis.

The percentage of degranulated ocular mast cells in five egg albumin--immunized, systemically challenged rats was compared with that in five egg albumin--immunized, saline-challenged controls. For the lid and orbit, at least 100 mast cells per rat were evaluated. For the conjunctiva, tarsus, limbus, and episclera-sclera, at least 20 were evaluated. For the ciliary body and choroid, all mast cells in 15 sections separated by at least 15 micrometer were examined. The morphology of degranulated and intact mast cells was the same in the experimental and control animals, except for the change in granules. There were significantly more degranulated mast cells in most of the ocular tissues of rats undergoing systemic anaphylaxis than in tissues of controls rats; the increase in degranulated cells was especially striking in the choroid. We concluded that degranulation of mast cells is a measure of anaphylaxis, provided that the number of degranulated mast cells, and not simply the presence of such cells, is considered and compared with appropriate controls.