MULTIPLE NADPH-PRODUCING PATHWAYS CONTROL GLUTATHIONE (GSH) CONTENT IN RETINA
MULTIPLE NADPH-PRODUCING PATHWAYS CONTROL GLUTATHIONE (GSH) CONTENT IN RETINA
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DOI：
10.1016/s0014-4835(86)80013-6
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发表时间：
1986-11-01
影响因子：
3.4
通讯作者：
SOLOMON, F
中科院分区：
文献类型：
--
作者：
WINKLER, BS;DESANTIS, N;SOLOMON, F
谷胱甘肽（GSH）以及产生NADPH的途径和谷胱甘肽还原酶，提供了针对氧化剂的防御系统。 GSH的氧化导致刺激己糖单磷酸分流并增加NADPH的产生。我们已经问，在暴露于氧化剂的大鼠视网膜暴露后，是否需要己糖单磷酸分流活性才能恢复GSH。通过耗尽己糖储存的视网膜，己糖单磷酸分流活性降低，然后将组织暴露于Diamide（0.04-1.0 mm），一种GSH的氧化剂，持续30分钟。将视网膜转移到含葡萄糖或无葡萄糖恢复培养基30分钟的情况下。对照视网膜保存在无葡萄糖，氧化培养基（无二酰胺）中，持续90-120分钟，在与葡萄糖孵育的视网膜中发现的90％的Main GSH。将己糖耗尽的视网膜暴露于0.4毫米酰胺后，观察到GSH降低了近90％。当去除氧化剂时，在存在或不存在葡萄糖的情况下，GSH的水平返回到控制值的80％以上。相比之下，如果将视网膜转移到有或没有葡萄糖的冰冷（1-5.Degree.c）培养基中，或者如果将视网膜转移到带有或不使用葡萄糖的冰冷（1-5.Degree.c）培养基中，或者用2 mm 1,3-预处理视网膜，则无法恢复GSH。 Bis（2-氯乙基）-1-硝基库（BCNU）抑制谷胱甘肽还原酶。两种产生NADPH的胞质酶的测量，即NADP+依赖性的MALIC酶和NADP+依赖性的异位酸异位酸盐脱氢酶，显示出较高的活性。来自苹果酶的NADPH的最佳产生为0.90 nmol NADPH，每个视网膜产生最小值，而使用异氯酸酯脱氢酶的平均速率为6.9 nmol NADPH，每个视网膜产生的最小值。我们建议这些酶以及长寿命的内源性底物（可能是谷氨酸）负责在己糖消耗的视网膜中恢复GSH。目前的结果表明，多个产生NADPH的系统能够控制视网膜中的GSH浓度。集中于己糖单磷酸根途径的研究是视网膜和其他组织中谷胱甘肽还原酶的唯一来源，这可能需要根据特定组织的整体代谢能力和底物利用来重新评估。因此，目前的发现不仅在视网膜方面很重要，而且对于其他组织，这些代谢特征与在视网膜中发现的特征相似。
Glutathione (GSH), together with NADPH-producing pathways and glutathione reductase, provides a defense system against oxidants. Oxidation of GSH causes stimulation of the hexose monophosphate shunt and increased production of NADPH. We have asked if hexose monophosphate shunt activity is required for the recovery of GSH following exposure of the isolated rat retina to an oxidant. Hexose monophosphate shunt activity was decreased by depleting the retina of hexose stores, before exposing the tissue to diamide (0.04-1.0 mM), an oxidant for GSH, for 30 min. Afte rexposure, retinas were transferred to either glucose-containing or glucose-free recovery medium for an additional 30 min. Control retinas kept in glucose-free, oxygenated medium (no diamide) for 90-120 min mainained GSH at 90% of the value found in retinas incubated with glucose. After exposure of hexose-depleted retinas to 0.4 mM diamide, a nearly 90% decrease in GSH was observed. When the oxidant was removed, the level of GSH returned to more than 80% of the control value in the presence or absence of glucose. In contrast, no recovery of GSH was observed after diamide treatment if the retinas were transferred to ice-cold (1-5.degree.C) media with or without glucose or if the retinas were pre-treated with 2 mM 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) to inhibit glutathione reductase. Measurements of two NADPH-producing cytosolic enzymes, namely NADP+-dependent malic enzyme and NADP+-dependent isocitrate dehydrogenase, revealed high activities. Optimum production of NADPH from malic enzyme was 0.90 nmol NADPH produced min-1 per retina, while with isocitrate dehydrogenase the average rate was 6.9 nmol NADPH produced min-1 per retina. We suggest that these enzymes together with a long-lived endogenous substrate (probably glutamate) are responsible for the recovery of GSH in hexose-depleted retinas. The present results suggest that more than one NADPH-producing system is capable of controlling the GSH concentration in retina. Studies that have focused on the hexose monophosphate shunt pathway as the sole source of NADPH for glutathione reductase in retina and other tissues may require re-evaluation depending on the overall metabolic capacity and substrate utilization of the particular tissue. Thus, the present findings are significant not only with respect to the retina but also for other tissues those metabolic characteristics are similar to those found in the retina.