Cejková Jitka, Vejrazka Martin, Pláteník Jan, Stípek Stanislav
Department of Eye Histochemistry, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Vídenská 1083, CZ-14220 Prague 4, Czech Republic.
Exp Gerontol. 2004 Oct;39(10):1537-43. doi: 10.1016/j.exger.2004.08.006.
The activities of superoxide dismutase, glutathione peroxidase (GPX) and catalase--the enzymatic scavengers of reactive oxygen species and the activities of xanthine oxidoreductase and xanthine oxidase, an enzyme known to generate reactive oxygen species, were studied in the corneas of normal rabbit eyes of various ages (1 month--young eyes; 4-9.5 months--young adult eyes; 2.0-2.75 years--middle aged eyes; 3.0-5.0 years--aged eyes). The activities of GPX, superoxide dismutase, xanthine oxidoreductase and xanthine oxidase were investigated biochemically in the scraped corneal epithelium. Catalase activity was detected histochemically in the corneal epithelium and endothelium. The results show that young corneas revealed lower activities of all the antioxidant enzymes investigated than did young adult corneas, in which enzymatic activities reached their maximum. In middle-aged corneas, GPX and catalase activities remained approximately at the same levels as seen in young adult corneas, whereas superoxide dismutase activity was decreased. In aged corneas, the activities of all antioxidant enzymes were dramatically decreased or even lost (catalase activity in the corneal endothelium). In contrast, xanthine oxidoreductase activity only slightly decreased with age and the xanthine oxidase proportion of total xanthine oxidoreductase remained unchanged. GPX, superoxide dismutase and catalase are important antioxidant enzymes protecting the cornea against the oxidative damage. Because the activities of these enzymes are lower in young animals and greatly reduced in aged animals, it is suggested that young and particularly aged corneas might be more susceptible to oxidative stress than are young adult corneas. This presumption is supported by the fact that the activities of prooxidant enzymes (xanthine oxidoreductase/xanthine oxidase) are only slightly decreased in aged corneas as compared to young adult corneas so that some imbalance between antioxidant and prooxidant enzymes exists already in the normal aged corneas.
研究了超氧化物歧化酶、谷胱甘肽过氧化物酶（GPX）和过氧化氢酶（活性氧的酶促清除剂）的活性，以及黄嘌呤氧化还原酶和黄嘌呤氧化酶（一种已知可产生活性氧的酶）的活性，研究对象为不同年龄的正常兔眼角膜（1个月大——幼眼；4 - 9.5个月大——青年成体眼；2.0 - 2.75岁——中年眼；3.0 - 5.0岁——老年眼）。采用生化方法研究了刮取的角膜上皮中GPX、超氧化物歧化酶、黄嘌呤氧化还原酶和黄嘌呤氧化酶的活性。通过组织化学方法检测了角膜上皮和内皮中的过氧化氢酶活性。结果显示，与酶活性达到最高水平的青年成体角膜相比，幼龄角膜中所研究的所有抗氧化酶活性均较低。在中年角膜中，GPX和过氧化氢酶活性与青年成体角膜中的水平大致相同，而超氧化物歧化酶活性降低。在老年角膜中，所有抗氧化酶的活性均显著降低甚至丧失（角膜内皮中的过氧化氢酶活性）。相比之下，黄嘌呤氧化还原酶活性仅随年龄略有降低，且黄嘌呤氧化酶在总黄嘌呤氧化还原酶中所占比例保持不变。GPX、超氧化物歧化酶和过氧化氢酶是保护角膜免受氧化损伤的重要抗氧化酶。由于这些酶的活性在幼龄动物中较低，在老龄动物中大幅降低，因此提示幼龄尤其是老龄角膜可能比青年成体角膜更容易受到氧化应激的影响。这一推测得到以下事实的支持：与青年成体角膜相比，老龄角膜中促氧化酶（黄嘌呤氧化还原酶/黄嘌呤氧化酶）的活性仅略有降低，因此在正常老龄角膜中抗氧化酶和促氧化酶之间已存在某种失衡。
