Prostaglandin synthesis, inhibition, and intraocular pressure.

Arachidonic acid, a precursor of prostaglandin E!} administered topically to rabbit and monkey eyes in concentrations of 0.2 to 20 per cent, or intravenously to rabbits in doses of 10 to 20 mg., produced a significant elevation of intraocular pressure. A dose-response relationship was demonstrated. Facility of outflow and anterior chamber aqueous protein were significantly higher in eyes treated topically with 2 per cent arachidonic acid than fellow control eyes. These effects of arachidonic acid were similar to those of prostaglandin E applied topically. Pretreatment with indomethacin, given intraperitoneally in doses of 10 mg. per kilogram or greater, or aspirin, as a 600 mg. suppository, prevented completely the elevation of intraocular pressure produced by two drops of 2 per cent arachidonic acid applied to the eyes of rabbits. The elevation of anterior chamber aqueous protein induced by topically applied 2 per cent arachidonic acid also was blocked by prior administration of indomethacin. Indomethacin and aspirin, inhibitors of prostaglandin synthesis from arachidonic acid, had no effect on the rise of intraoctdar pressure seen after instilling 5 fig of prostaglandins Et or Et.