The influence of topical corticosteroid therapy upon polymorphonuclear leukocyte distribution, vascular integrity and ascorbate levels in endotoxin-induced inflammation of the rabbit eye.

An acute inflammatory response was initiated in the rabbit eye by an intravitreal injection of bacterial endotoxin. We examined the effect of topical corticosteroid therapy upon polymorphonuclear leukocyte (PMN) infiltration into the eye, protein leakage into aqueous humor and ascorbate level in aqueous humor. Corticosteroid therapy initiated prior to injection of endotoxin suppresses the clinical signs of inflammation, partially prevents the fall in aqueous-humor ascorbate level, has little effect upon protein leakage, but markedly reduces PMN infiltration. Corticosteroid therapy initiated after the injection of endotoxin also suppresses the clinical signs of inflammation, reduces the fall in ascorbate levels and does not influence protein leakage. However, in this case there is a marked persistence of PMN infiltration into ocular tissues. Thus the number of PMNs present in the ocular tissues is little different from that in non-steroid treated control eyes, although the clinical signs of inflammation are reduced. We suggest that in the clinical situation, the initial anti-inflammatory activity of the corticosteroids is related to an inhibitory effect upon the activity of PMNs already within the tissues, which then prevents the ensuing cascade of characteristic inflammatory events.