Becker B F
Department of Physiology, University of Munich, Germany.
Free Radic Biol Med. 1993 Jun;14(6):615-31. doi: 10.1016/0891-5849(93)90143-i.
Uric acid, or more correctly (at physiological pH values), its monoanion urate, is traditionally considered to be a metabolically inert end-product of purine metabolism in man, without any physiological value. However, this ubiquitous compound has proven to be a selective antioxidant, capable especially of reaction with hydroxyl radicals and hypochlorous acid, itself being converted to innocuous products (allantoin, allantoate, glyoxylate, urea, oxalate). There is now evidence for such processes not only in vitro and in isolated organs, but also in the human lung in vivo. Urate may also serve as an oxidisable cosubstrate for the enzyme cyclooxygenase. As shown for the coronary system, a major site of production of urate is the microvascular endothelium, and there is generally a net release of urate from the human myocardium in vivo. In isolated organ preparations, urate protects against reperfusion damage induced by activated granulocytes, cells known to produce a variety of radicals and oxidants. Intriguingly, urate prevents oxidative inactivation of endothelial enzymes (cyclooxygenase, angiotensin converting enzyme) and preserves the ability of the endothelium to mediate vascular dilatation in the face of oxidative stress, suggesting a particular relationship between the site of urate formation and the need for a biologically potent radical scavenger and antioxidant.
尿酸，或者更准确地说（在生理pH值下），其单阴离子尿酸盐，传统上被认为是人体嘌呤代谢中一种无代谢活性的终产物，没有任何生理价值。然而，这种普遍存在的化合物已被证明是一种选择性抗氧化剂，尤其能够与羟基自由基和次氯酸反应，自身会转化为无害产物（尿囊素、尿囊酸、乙醛酸、尿素、草酸盐）。现在不仅在体外和离体器官中有证据表明存在此类过程，在人体肺部的体内实验中也有证据。尿酸盐还可能作为环氧化酶的可氧化共底物。正如在冠状动脉系统中所显示的，尿酸盐的主要产生部位是微血管内皮，并且在人体心肌体内通常存在尿酸盐的净释放。在离体器官制剂中，尿酸盐可保护免受活化粒细胞诱导的再灌注损伤，活化粒细胞是已知会产生多种自由基和氧化剂的细胞。有趣的是，尿酸盐可防止内皮酶（环氧化酶、血管紧张素转换酶）的氧化失活，并在面对氧化应激时保持内皮介导血管舒张的能力，这表明尿酸盐形成部位与对具有生物活性的自由基清除剂和抗氧化剂的需求之间存在特殊关系。
