Intercellular junctions of the ciliary epithelium in anterior uveitis

The intercellular junctions of the anterior ciliary and iridial epithelia of the inflamed rabbit eye were examined by use of an ultrastructural tracer, conventional electron microscopy, and the freeze-fracture technique. In normal control eyes, intravascularly injected horseradish peroxidase was prevented from entering the posterior chamber by the zonulae occludentes of the nonpigmented ciliary epithelium. In freeze-fracture studies these junctions appeared as a series of 5-12 branching and anastomosing strands on the P-fracture face, which were complemented by a network of shallow grooves with discontinuous rows of particles at their bases on the E-fracture face. Gap junctions were abundant, particularly between the apical surfaces of the pigmented and nonpigmented layers where they were accompanied by discontinuous tight junctional strands. In eyes inflamed by intravitreal injection of E. coli 055:B55 endotoxin, peroxidase leaked into the posterior chamber primarily from the crests of anterior ciliary and iridial processes. Freeze-fracture electron microscopy of these same areas demonstrated primarily a simplification in junctional complexity and reduction in the number of occluding strands. Severe junctional disorganization and complete junctional fragmentation were rarely seen. A profound reduction in the complement of gap junctions was observed particularly between the apical surfaces of the pigmented and nonpigmented layers. The possible functional significance of the observed changes is discussed.