ASCORBIC ACID

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。我们的数据表明晶状体周围液体的相对缺氧对于保护晶状体免受最常见的老年性白内障的侵害是很重要的。玻璃体凝胶的破坏导致晶状体暴露于氧气的增加和核性白内障的形成。我们在接受视网膜手术的患者的眼睛中检测到氧气梯度，这预示着玻璃体一定在消耗氧气。对分离玻璃体的耗氧量的直接试验证实了这一预测，并证明这种作用不依赖于细胞代谢活动，而依赖于抗坏血酸。先前对兔子的研究表明，抗坏血酸通过房水进入眼睛，滋养眼睛前部的结构（房水中的抗坏血酸浓度比血液中的浓度高20倍）。人们认为眼后部的抗坏血酸是由房水扩散而来的。然而，与其他物种不同的是，人类玻璃体内（眼后）的抗坏血酸含量高于房水内（眼前）的抗坏血酸含量，这就排除了房水作为人类玻璃体抗坏血酸唯一来源的可能性。为了更好地了解抗坏血酸在眼睛中的分布，从而了解抗坏血酸的来源和吸收，我们想测量活兔子和人眼睛中的抗坏血酸梯度。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our data suggest that the relative hypoxia in the fluids around the lens is important to protect the lens against the most common type of age-related cataract. Destruction of the vitreous gel leads to increased exposure of the lens to oxygen and the formation of nuclear cataracts. We detected oxygen gradients in the eyes of patients undergoing retinal surgery that predicted that the vitreous body must be consuming oxygen. Direct tests of oxygen consumption in isolated vitreous humor confirmed this predication and demonstrated that this effect was independent of cellular metabolic activity and dependent on ascorbate. Previous studies in rabbits have suggested that ascorbate enters the eye in the aqueous humor that nourishes the structures of the anterior of the eye (ascorbate concentrations in aqueous humor are >20X greater than in the blood). It was believed that ascorbate in the posterior of the eye was derived by diffusion from the aqueous humor. However, unlike other species, humans have higher ascorbate in the vitreous humor (in the posterior of the eye) than in the (anterior) aqueous humor, ruling out the aqueous as the sole source of ascorbate for the human vitreous. To get a better idea of the ascorbate distribution in the eye and, therefore, the sources and sinks for ascorbate, we would like to measure ascorbate gradients in the eyes of living rabbits and humans.