Department of Ophthalmology and Visual Sciences, Washington University, Saint Louis, MO 63110, USA.
Philos Trans R Soc Lond B Biol Sci. 2011 Apr 27;366(1568):1293-300. doi: 10.1098/rstb.2010.0228.
The lens is composed of a thin metabolically active outer layer, consisting of epithelial and superficial fibre cells. Lying within this outer shell are terminally differentiated, metabolically inactive fibre cells, which are divided into an outer cortex and central nucleus. Mature fibre cells contain a very high protein concentration, which is important for the transparency and refractive power of the lens. These proteins are protected from oxidation by reducing substances, like glutathione, and by the low-oxygen environment around the lens. Glutathione reaches the mature fibre cells by diffusing from the metabolically active cells at the lens surface. With age, the cytoplasm of the nucleus becomes stiffer, reducing the rate of diffusion and making nuclear proteins more susceptible to oxidation. Low pO(2) is maintained at the posterior surface of the lens by the physical and physiological properties of the vitreous body, the gel filling the space between the lens and the retina. Destruction or degeneration of the vitreous body increases exposure of the lens to oxygen from the retina. Oxygen reaches the lens nucleus, increasing protein oxidation and aggregation and leading to nuclear cataract. We suggest that maintaining low pO(2) around the lens should prevent the formation of nuclear cataracts.
晶状体由一层薄的代谢活跃的外层组成，包括上皮细胞和浅层纤维细胞。在这个外壳内是终末分化的、代谢不活跃的纤维细胞，它们分为外皮层和中央核。成熟的纤维细胞含有非常高的蛋白质浓度，这对于晶状体的透明度和屈光力非常重要。这些蛋白质被还原物质如谷胱甘肽和晶状体周围的低氧环境所保护，免受氧化。谷胱甘肽通过从晶状体表面的代谢活跃细胞扩散到达成熟的纤维细胞。随着年龄的增长，核的细胞质变得更加僵硬，降低了扩散速度，使核蛋白更容易氧化。玻璃体的物理和生理特性在晶状体的后表面维持低 pO(2)，玻璃体是填充在晶状体和视网膜之间的凝胶。玻璃体的破坏或变性会增加视网膜对晶状体的氧气暴露。氧气到达晶状体核，增加蛋白质氧化和聚集，导致核性白内障。我们认为，保持晶状体周围的低 pO(2)应该可以防止核性白内障的形成。
