Synthesis of prostaglandin E in rabbit eyes with topically applied epinephrine.

Using radioimmunoassay techniques, we measured the amounts of prostaglandin E (PGE) in the aqueous humor and vitreous body of 22 phakic and ten aphakic rabbit eyes. Either epinephrine and placebo, epinephrine and indomethacin, indomethacin and placebo, or placebo and placebo were administered topically for 5 months. Treatment of aphakic eyes was initiated 1 month after intracapsular lens extraction. Topically applied epinephrine apparently induced the synthesis of prostaglandin, manifested by elevated PGE in the aqueous and vitreous. Phakic eyes treated with epinephrine and placebo had mean PGE levels of 407.33 pg/ml in the aqueous and 177.0 pg/ml in the vitreous, whereas control eyes given only placebo had mean levels of 165.83 in aqueous and 59.17 in vitreous. Topically applied indomethacin inhibited epinephrine-induced synthesis of PGE in the aqueous humor, but had no significant effect in the vitreous. PGE levels, higher in placebo-treated aphakic eyes than in phakic ones, were elevated further by epinephrine treatment (from 388.40 to 1851.60 pg/ml in aqueous of aphakic eyes, and from 236.40 to 850.60 pg/ml in vitreous also of aphakic eyes). Our findings relate to the pathogenesis of epinephrine-induced maculopathy and to the mechanism of the ocular hypotensive effect of epinephrine.