The effects of prostaglandins on the blood-ocular barrier

The effects of prostaglandins (PGs) and PG-related compounds on the blood-ocular barriers were examined using pigmented rabbits. Latanoprost (PhXA41), PGF2(alpha)-isopropyl ester (PGF2(alpha)-IE) or PGE2 was topically applied once only or once daily for 8 weeks. Aqueous flare was measured with a laser flare-cell meter, and morphological changes in the ciliary processes after repeated applications of a test drug were investigated by means of light or electron microscopy using horseradish peroxidase (HRP) as a tracer. PGF2(alpha)-IE and PGE2, but not PhXA41, caused an initial rise in the aqueous flare after application. On the other hand, no morphological changes were found in the ciliary processes after 8-week PhXA41 application. After 8-week application of PGF2(alpha)-IE or PGE2 dilation of ciliary channels in the ciliary processes were found. Leakage of intravenously injected fluorescein was measured by a vitreous fluorophotometer after an intravitreal injection of PGE2, PGF2(alpha), or PhXA41. Vitreous fluorescence was significantly higher in treated eyes than in controls after intravitreal injection of PGE2 or PGF2(alpha), while it showed no significant change after intravitreal injection of PhXA41. Only PGE2 caused morphological changes in the retina. These results suggest that PhXA41 does not compromise the integrity of the blood-ocular barriers, and has a potential as a future anti-glaucoma eyedrop.