Giblin F J, Chakrapani B, Reddy V N
Invest Ophthalmol. 1976 May;15(5):381-93.
The relationship of the concentration of glutathione (GSH) in lens epithelium to the transport of cations in the lens was studied by decreasing the level of GSH in the epithelium and monitoring subsequent effects in the lens on the distribution of cations, the activity of Na+-K+ ATPase and the uptake and efflux of 86Rb. Oxidation of GSH in cultured rabbit lenses was accomplished by the use of 1 mM tertiary butyl hydroperoxide (TBHP), a reagent which appears to be suitable for the specific oxidation of GSH in this tissue. The concentration of GSH found in the normal lens epithelium was estimated to be 64 mum per gram wet weight or nearly six times that present in the whole lens. A decrease in the concentration of GSH in lens epithelium of 60 per cent or more leads to an increase in hydration, a shift in the distribution of Na+, K+, and Cl-, a decrease in the activity of Na+-K+ ATPase, and a decrease in the active transport, and an increase in the passive diffusion of 86Rb. In the TBHP-treated lenses there is a rapid decrease in the production of lactate, possibly as a result of the inhibition of Na+-K+ ATPase, but the effect on the level of lens ATP is delayed and less pronounced. It appears that the adverse effect on membrane permeability caused by the oxidation of GSH is partially reversed when a high level of GSH returns to the epithelium. However, the decrease in active transport of 86Rb and the inactivation of Na+-K+ ATPase are not reversed by either regeneration of GSH in the tissue or by treatment with exogenous dithiothreitol and may indicate an irreversible conformational change in the enzyme initiated by the loss of the protective effect of GSH. The data indicate that a critical level of GSH is required in the lens epithelium for the maintenance of normal cation transport.
通过降低晶状体上皮细胞中谷胱甘肽（GSH）的水平，并监测随后晶状体中阳离子分布、Na⁺-K⁺ ATP酶活性以及⁸⁶Rb摄取和流出的变化，研究了晶状体上皮细胞中GSH浓度与晶状体中阳离子转运的关系。通过使用1 mM叔丁基过氧化氢（TBHP）实现培养兔晶状体中GSH的氧化，TBHP似乎是适合该组织中GSH特异性氧化的试剂。正常晶状体上皮细胞中GSH的浓度估计为每克湿重64 μmol，几乎是整个晶状体中GSH浓度的六倍。晶状体上皮细胞中GSH浓度降低60%或更多会导致水合作用增加、Na⁺、K⁺和Cl⁻分布改变、Na⁺-K⁺ ATP酶活性降低、主动转运减少以及⁸⁶Rb被动扩散增加。在经TBHP处理的晶状体中，乳酸生成迅速减少，这可能是由于Na⁺-K⁺ ATP酶受到抑制，但对晶状体ATP水平的影响延迟且不明显。当高水平的GSH回到上皮细胞时，GSH氧化对膜通透性的不利影响似乎部分得到逆转。然而，⁸⁶Rb主动转运的减少和Na⁺-K⁺ ATP酶的失活，无论是通过组织中GSH的再生还是通过用外源性二硫苏糖醇处理都不能逆转，这可能表明由于GSH保护作用丧失引发了该酶不可逆的构象变化。数据表明，晶状体上皮细胞中需要临界水平的GSH来维持正常的阳离子转运。
