Williams R N, Paterson C A
Exp Eye Res. 1986 Jul;43(1):7-13. doi: 10.1016/s0014-4835(86)80041-0.
We have examined the influence of ascorbic acid on the generation of lipoxygenase products by the rabbit cornea, an avascular tissue which is continuously bathed by high concentrations of ascorbic acid present within the aqueous humor of the eye. Corneal homogenates were incubated with [14C]arachidonic acid and the resulting metabolites separated by thin-layer chromatography. The metabolites were then quantified by liquid scintillation counting techniques. The biosynthesis of the major lipoxygenase product formed by the cornea, 12-HETE, was significantly inhibited by physiological concentrations of ascorbic acid; PGE2 formation by the cornea was not altered in the presence of ascorbic acid. Furthermore, ascorbic acid inhibited the formation of 12-HETE in the presence of catalase, indicating that hydrogen peroxide generated by ascorbate was not responsible for diminishing the lipoxygenase activity of the cornea. However, high concentrations of hydrogen peroxide (10(-4) M) did inhibit the formation of 12-HETE by the corneal homogenates. Another antioxidant, 2,6-dichlorophenol-indophenol (10 micrograms ml-1), also inhibited the formation of 12-HETE by the cornea. Therefore, it appears that the inhibition of corneal lipoxygenase by ascorbic acid could be related to the antioxidant properties of this vitamin. These studies suggest that ascorbic acid within the aqueous humor might modulate lipoxygenase activity within the cornea.
我们研究了抗坏血酸对兔角膜脂氧合酶产物生成的影响。兔角膜是一种无血管组织，持续被眼房水中高浓度的抗坏血酸所浸润。将角膜匀浆与[14C]花生四烯酸一起孵育，然后通过薄层色谱法分离产生的代谢产物。接着采用液体闪烁计数技术对代谢产物进行定量分析。角膜生成的主要脂氧合酶产物12 - HETE的生物合成受到生理浓度抗坏血酸的显著抑制；在有抗坏血酸存在的情况下，角膜中PGE2的生成未发生改变。此外，在过氧化氢酶存在的情况下，抗坏血酸仍能抑制12 - HETE的生成，这表明抗坏血酸产生的过氧化氢并非导致角膜脂氧合酶活性降低的原因。然而，高浓度的过氧化氢（10(-4) M）确实能抑制角膜匀浆中12 - HETE的生成。另一种抗氧化剂2,6 - 二氯酚靛酚（10微克/毫升）也能抑制角膜中12 - HETE的生成。因此，抗坏血酸对角膜脂氧合酶的抑制作用可能与其作为维生素的抗氧化特性有关。这些研究表明，眼房水中的抗坏血酸可能会调节角膜内的脂氧合酶活性。
