Electron Microscopic Studies on the Blood‐aqueous Barrier of Prostaglandin‐treated Rabbit Eyes

Abstract

Prostaglandins E1 and E2 were applied topically to rabbit eyes. Structures related to the blood-aqueous barrier in the iridial and ciliary processes, as well as the permeability of the ciliary epithelium to the protein tracer horseradish peroxidase, were studied with the electron microscope. Marked morphological changes, including dilations of the intercellular spaces and separation of the two epithelial cell layers, were found in the epithelium of the iridial processes. Only minor structural changes were found in the epithelium of the ciliary processes. Leakage of peroxidase through the intercellular spaces of the epithelium was demonstrated in the iridial processes and in the anterior parts of the ciliary processes. In the ciliary vessels of the same regions, opening of interendothelial gaps, platelet aggregations, microthrombi, and haemorrhages were found. In a previous in vitro study on the effects of prostaglandins on the movement of peroxidase in the ciliary epithelium, no structural changes of the epithelium were found, and the epithelial diffusion barrier to peroxidase was found to be intact. It is assumed that the breakdown of this barrier in vivo is secondary to vascular changes.

Electron Microscopic Studies on the Blood‐aqueous Barrier of Prostaglandin‐treated Rabbit Eyes

“…The relatively sparse pathological findings in the iris vessels in the PGtreated eyes are in contrast to the marked vascular changes found in the vessels of the iridial and ciliary processes described in the preceding paper (Pedersen 1975). This may be due to differences in structure of these vessels.…”

“…Iris tissue was obtained from the same eyes used in the preceding work (Pedersen 1975). The reader is referred to this paper for details concerning the material and methods.…”

“…By leakage of HRP through the ciliary epithelium (Pedersen 1975), the concentration of the tracer in the aqueous humour will increase during the period from the HRP-injection to the enucleation. However, diffusion of HRP from the aqueous humour into the iris stroma, via the anterior surface of iris, seems to be of minor significance.…”

“…Leakage of the protein tracer HRP across the barrier is found in the ciliary epithelium (Pedersen 1975) and in iris vessels. Thus, these PGs induce some of the changes found in experimental immunogenic uveitis (Pedersen 1973, 74a, 74b).…”

“…4). In some places, the internal limiting membrane covering the epithelium contained HRP, which apparently had spread from leakage sites in the ciliary epithelium (Pedersen 1975).…”