Intercellular junctions of the iris epithelia in Macaca mulatta.

The intercellular junctions in the anterior myoepithelium and posterior pigmented epithelium of the rhesus monkey iris were examined using an ultrastructural tracer, conventional electron microscopy, and the freeze-fracture technique. Within the anterior myoepithelium the lateral cell margins were joined by puncta adhaerentia, desmosomes, and gap junctions. The distribution of the puncta adhaerentia and desmosomes was restricted to the apico-lateral region of these cells. Joining the apical surface of the anterior myoepithelium and posterior pigmented epithelium gap junctions, puncta adhaerentia, and desmosomes also were present. Adjacent posterior pigmented epithelial cells were joined by an apico-lateral junctional complex, which consisted of a zonula occludens, zonula adhaerens, and gap junction. These cells also were connected by one or more desmosomes. Intravenously injected horseradish peroxidase, which diffused from the ciliary body stroma, was prevented from reaching the posterior chamber by the presence of the zonulae occludentes between adjacent posterior pigmented epithelial cells. Their presence was confirmed using the double replica method of freeze-fracturing. The zonulae occludentes appeared as a continuous series of branching and anastomosing strands of particles on the P-fracture face, which were complemented on the E-fracture face by a series of shallow grooves. These junctions varied in complexity from one to eight or more strands indicating that they are analogous in both location and degree of permeability to the zonulae occludentes present in the nonpigmented ciliary epithelium.