Chapter 2 Ocular Aquaporins and Aqueous Humor Dynamics

Abstract

Publisher Summary Vision is dependent upon the efficient movement of water among and within various structures of the eye. To facilitate the faithful transmission of light rays from the corneal surface to the retinal photoreceptors, the eye is pressurized, having three compartments that are filled with optically transparent fluids: vitreous humor occupies ∼80% of the interior volume of the eye and lies between the posterior face of the lens and the retina; aqueous humor fills the other two compartments, the anterior and posterior chambers, located on either side of the iris. The circulation of aqueous humor from the posterior to the anterior chamber (and then out of the eye) enables the delivery of nutrients and removal of waste products from two specialized avascular tissues, the cornea and crystalline lens that function to focus light onto the retina. The clarity of these two organic lenses, and thus their ability to refract light, is exquisitely dependent upon water homeostasis within and the circulation of aqueous humor around their structures. This chapter reviews data that characterize the role of aquaporins in the movement of water into and out of the eye (aqueous humor dynamics). First, it provides an overview of aquaporin discovery and its molecular structure and function in cellular membranes. Second, it summarizes the specific distribution of aquaporin homologues in the eye. Third, it discusses the specific role of aquaporin channels in aqueous humor dynamics. Finally, the chapter discusses the future direction of aquaporin research in aqueous humor dynamics and the potential of aquaporins as drug targets.