Mostafapour M K, Schwartz C A
Invest Ophthalmol Vis Sci. 1982 May;22(5):606-12.
With the use of a freeze-sectioning technique, the existence of a centripetal protein gradient in the rabbit lens is demonstrated. The steepness of this gradient (the difference in the protein concentration between periphery and the center) varies with age: it increases from a value of 40% in 6- to 8-month-old lenses to 60% by the age of 4 to 5 years and then begins to decline at an average rate of about 5% per year, reaching a value below 40% in 9-year-old lenses. The decline in protein concentration gradient is reciprocated by a gain in the water content. Electrophoretic evidence shows that the decline in the protein gradient is preceded and accompanied by postsynthetic modification of lens crystallin polypeptides. Modifications result in the formation of crosslinked material that stays on the top of sodium dodecyl sulfate gels and of degraded polypeptides with molecular weights below 20,000 daltons. It is hypothesized that the protein gradient comes about probably because lens crystallins are capable of making extensive surface contacts to produce a tightly packed matrix. As the lens ages, post-synthetic modifications and hydrolytic breakdown produce a gradual disorganization in these structural proteins. Local or general disorganization will allow water to fill the gaps and produce hydration, which could predispose the lens to opacity formation.
通过使用冷冻切片技术，证明了兔晶状体中存在向心蛋白梯度。这种梯度的陡度（周边与中心之间蛋白质浓度的差异）随年龄变化：从6至8月龄晶状体中的40%增加到4至5岁时的60%，然后开始以每年约5%的平均速率下降，在9岁晶状体中降至40%以下。蛋白质浓度梯度的下降与含水量的增加相对应。电泳证据表明，蛋白质梯度的下降在晶状体结晶多肽的合成后修饰之前并伴随其发生。修饰导致形成停留在十二烷基硫酸钠凝胶顶部的交联物质以及分子量低于20,000道尔顿的降解多肽。据推测，蛋白质梯度的形成可能是因为晶状体结晶能够进行广泛的表面接触以产生紧密堆积的基质。随着晶状体老化，合成后修饰和水解分解会导致这些结构蛋白逐渐紊乱。局部或整体紊乱会使水填充间隙并产生水合作用，这可能使晶状体易于形成混浊。
