Chapter 2 Molecular Approaches to the Study of the Na+,K+ -ATPase and Chloride Channels in the Ocular Ciliary Epithelium

Abstract

The ocular ciliary epithelium is a bilayer of neuroepithelial cells with a unique configuration in the mammalian eye and possibly in the entire human body. The bilayer consists of two secretory polarized epithelial cells—the nonpigmented epithelial (NPE) and pigmented epithelial (PE) cells—opposing each other at their apical plasma membranes. This unusual configuration is intriguing and has hampered progress in understanding the way the ciliary epithelium regulates the secretion of aqueous humor into the posterior chamber of the eye. The generally accepted theory that the ciliary epithelium is the site of secretion of aqueous humor is based on anatomical and physiological evidence. Along the ocular ciliary epithelium, several distinct anatomical regions have been defined based on the morphological characteristics of the NPE and PE cells. The pars plicafa, which is the most anterior region of the ciliary epithelium, is distinguished by numerous folding processes providing a large transport surface area.