Effects of pilocarpine and paracentesis on occluding junctions between the nonpigmented ciliary epithelial cells

Abstract

The occluding junctions between the nonpigmented ciliary epithelial cells in the Rhesus monkey have been studied with the electron microscope using horseradish peroxidase as a tracer and the freeze-fracture technique. These junctions can be divided into two distinct classes: one type is made of parallel strands, while the other type consists of a net-like meshwork of junctional strands. The occluding junctions in the pars planar and the valley of the ciliary process are mainly of the parallel type which is composed of between three and 15 strands. After pilocarpine instillation, the straight and parallel strands in these portions became wavy but remained intact. This finding suggests that during accomodation the blood-aqueous barrier is maintained by changing the shape of the occulding junctions so as to resist the contraction of the ciliary muscle. The second type of junctional strands, made up of from five to 18 ridges and grooves, is mainly seen in the crest of the ciliary process. Following repeated paracentesis, every ciliary process of almost all the experimental monkeys developed cysts in the ciliary processes but only at their most anterior portion. The cyst walls were ruptured at several locations. The cysts, the intercellular spaces and the posterior chamber contained fibrin. In freeze-fractured replicas of these specimens, the occluding junctions at the anteriormost portion of the pars plicata were normally composed of from one to five strands of the parallel type, and which were often fragmented after paracentesis. This observation indicates that the occluding junctions in this portion of the ciliary process may be responsible for the leakage of the serum protein into the posterior chamber that is observed after paracentesis.