Increased vascular permeability in the rabbit iris induced by prostaglandin E1. An electron microscopic study using lanthanum as a tracer in vivo.

Prostaglandin E1 (PGE1) (25 micrograms) was applied topically to the eyes of albino rabbits, and lanthanum was used as an electron microscopic tracer to study possible vascular permeability changes in the iris of these eyes. Lanthanum was injected directly into the blood circulation 15 min after application of the PG, and the eyes were enucleated 30 to 60 min later. PGE1 was found to induce increased vascular permeability. Heavy deposits of the tracer were found in the walls of iridial venules, especially between the endothelium and its basement lamina. The highest concentration of lanthanum was found in close relation to the interendothelial clefts. Occasionally, gaps between neighbouring endothelial cells were observed. In control eyes, not treated with PG, no extravasation of the tracer was found. The study indicates that the iridial blood vessels contribute to the production of the plasmoid aqueous humour induced by PGE1 in the rabbit eye.