The effects of intravenous and intraocular injections of Shigella endotoxin on the inflammatory response, the release of prostaglandin-like substances into the aqueous humour, and the effects of indomethacin on the inflammatory response were studied in the rabbit eye. 2. Both intravenous and intraocular injection of endotoxin released 12.8 ng to 72 ng of prostaglandin-like substances per ml of aqueous humour and increased the permeability of the blood-aqueous barrier as shown by the rise in aqueous humour protein (26-52 mg protein/ml of aqueous humour). 3. Indomethacin, 0.25% administered topically completely inhibited the release of prostaglandin-like substances but was found to have inconsistent inhibitory effects on the clinical signs of inflammation and on the blood-aqueous barrier. Indomethacin was less effective in eyes receiving the higher dose of endotoxin. 4. It is suggested that prostaglandins and possibly other chemical mediators are involved in endotoxin-induced ocular inflammation.
