Freeze-fracture analysis of junctional complexes in human ciliary epithelia.

The junctions connecting the epithelial cells of the human ciliary body were studied on replicas of freeze-fractured preparations. Gap junctions are present at the lateral surfaces of the cells of the pigmented epithelium. Gap junctions, isolated linear strands and desmosomes are found between the apical surfaces of pigmented and non-pigmented epithelial cells. Gap junctions, zonulae occludentes and desmosomes join the lateral surfaces of the non-pigmented epithelial cells. These findings suggest that the blood-aqueous barrier is located at the level of the zonulae occludentes of the non-pigmented epithelial cells. This is consistent with previous studies using thin sections and tracer substances. The function of the many gap junctions connecting the cells of the two epithelial layers is obscure since their presence is not consistent with electrophysiological data from this region.