Institute for Cardiological Investigations A.C. Taquini, University of Buenos Aires and CONICET, Marcelo T. de Alvear 2270, Buenos Aires, Argentina.
Mol Aspects Med. 2012 Oct-Dec;33(5-6):638-41. doi: 10.1016/j.mam.2012.07.016. Epub 2012 Jul 20.
Water is a major component of the eye, and water channels (aquaporins) are ubiquitous in ocular tissues, and quite abundant at their different locations. AQP1 is expressed in corneal endothelium, lens epithelium, ciliary epithelium, and retinal pigment epithelium. AQP3 is expressed in corneal epithelium, and in conjunctival epithelium. AQP4 is expressed in ciliary epithelium and retinal Muller cells. AQP5 is expressed in corneal epithelium, and conjunctival epithelium. AQP0 is expressed in lens fiber cells. It is known that five ocular tissues transport fluid, namely: (1) Corneal endothelium; (2) Conjunctival epithelium; (3) Lens epithelium; (4) Ciliary epithelium; (5) Retinal pigment epithelium. For the corneal endothelium, aquaporins are not the main route for trans-tissue water movement, which is paracellular. Instead, we propose that aquaporins allow fast osmotic equilibration of the cell, which is necessary to maintain optimal rates of fluid movement since the cyclic paracellular water transfer mechanism operates separately and tends to create periodic osmotic imbalances (τ∼5 s).
水是眼睛的主要组成部分，水通道（水通道蛋白）在眼部组织中无处不在，在不同的部位含量相当丰富。AQP1 表达于角膜内皮、晶状体上皮、睫状上皮和视网膜色素上皮。AQP3 表达于角膜上皮和结膜上皮。AQP4 表达于睫状上皮和视网膜 Muller 细胞。AQP5 表达于角膜上皮和结膜上皮。AQP0 表达于晶状体纤维细胞。已知有五种眼部组织可转运液体，分别是：（1）角膜内皮；（2）结膜上皮；（3）晶状体上皮；（4）睫状上皮；（5）视网膜色素上皮。对于角膜内皮来说，水通道蛋白并不是跨组织水运动的主要途径，而是通过细胞旁途径。相反，我们提出水通道蛋白允许细胞快速达到渗透平衡，这对于维持最佳的液体运动速率是必要的，因为周期性的细胞旁水转运机制是独立运作的，并且容易造成周期性的渗透失衡（τ∼5 s）。
