Corneal transport of circulating glutathione in normal and galactosemic guinea pigs.
Corneal transport of circulating glutathione in normal and galactosemic guinea pigs.
复制标题
正常和半乳糖血症豚鼠循环谷胱甘肽的角膜转运。
DOI：
10.1097/00003226-199905000-00014
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发表时间：
1999
期刊：
影响因子：
2.8
通讯作者：
Zlokovic,BV
中科院分区：
文献类型：
--
作者：
Kannan,R;Mackic,JB;Zlokovic,BV
目的：为研究豚鼠角膜谷胱甘肽（GSH）的合成和转运，以及半乳糖喂养和生长对GSH转运的影响，采用半乳糖饲料喂养豚鼠10 d，测定豚鼠角膜GSH稳态水平和最大合成速率（GSH-SR）。通过使用原位眼灌注模型，在正常豚鼠中测量[35 S] GSH（4 nM）和[14 C]蔗糖的角膜转运作为时间（1-10 min）的函数，|gg-谷氨酰转肽酶（GGT）抑制和未抑制条件。GSH摄取的单向常数被确定为灌流液中GSH浓度的函数。在对照组和喂食半乳糖10天的豚鼠中测定了半乳糖喂养对角膜摄取示踪剂GSH的影响。结果：对照组豚鼠角膜GSH水平（nmol/mg蛋白）为47.6，半乳糖组为36.4（p< 0.05）;两组的GSH-SR无显著差异（分别为1.98和2.27 nmol/min/mg蛋白; p= NS）。角膜对示踪剂[35 S] GSH（4 nM）的摄取在10 min内呈线性，并且比不可渗透标记物[14 C]蔗糖的摄取高几倍。GSH的单向速率常数（经蔗糖校正）为4.03+/-0.21 x 10-3/min。正常豚鼠的GSH摄取是一个饱和过程，Km为24+/-4 [micro] M，Vmax为92+/-14 pmol/min/g，60 [micro] M浓度的GSH和GSH单乙酯显著抑制GSH摄取。与对照组相比，半乳糖喂养的豚鼠角膜对示踪剂GSH的摄取显著降低（几乎与蔗糖的摄取相同）。10日龄和4周龄豚鼠角膜GSH摄取相似，而9月龄豚鼠角膜GSH摄取显著降低（~ 80%）。结论：年轻成年豚鼠角膜细胞摄取GSH是载体介导的，其机制与转肽途径无关。循环GSH的可用性降低可能是与衰老和由于相对GSH缺乏引起的角膜水合相关的角膜病理学发展的重要因素。
Purpose: To study synthesis and transport of glutathione (GSH) in guinea-pig cornea and to determine the effect of galactose feeding and growth on transport.Methods: Steady-state level and maximal rate of synthesis of GSH (GSH-SR) were determined in guinea pigs fed 50% galactose diet for 10 days and in controls. By using a model of in situ eye perfusion, corneal transport of [35S] GSH (4 nM) and [14C] sucrose was measured as a function of time (1-10 min) in normal guinea pigs under| gg-glutamyltranspeptidase (GGT)-inhibited and uninhibited conditions. The unidirectional constant of GSH uptake was determined as a function of GSH concentration in the perfusate. The effect of galactose feeding on corneal uptake of tracer GSH was determined in control and 10-day galactose-fed guinea pigs. Levels of GSH and uptake of GSH also were measured in corneas from three different age groups: 10 days, 4 weeks, and 9 months.Results: The mean GSH level (nmol/mg protein) in corneas of control guinea pigs was 47.6, which decreased to 36.4 (p< 0.05) in 10-day galactose-fed animals. The GSH-SR was not significantly different in the two groups (1.98 vs. 2.27 nmol/min/mg protein, respectively; p= NS). Corneal uptake of tracer [35S] GSH (4 nM) was linear up to 10 min and was several-fold higher than that of the impermeable marker [14C] sucrose. The unidirectional rate constant (corrected for sucrose) for GSH was 4.03+/-0.21 x 10-3/min. GSH uptake in normal guinea pigs occurred by a saturable process with a Km of 24+/-4 [micro] M and Vmax of 92+/-14 pmol/min/g and was significantly inhibited by GSH and GSH monoethyl ester at 60 [micro] M concentrations. Corneal uptake of tracer GSH in galactose-fed guinea pigs showed a dramatic decrease (almost to that of sucrose) as compared with control guinea pigs. GSH uptake was similar in corneas of 10-day and 4-week-old guinea pigs, whereas that in 9-month-old guinea pigs showed a significant (~ 80%) decrease in uptake.Conclusion: Cellular uptake of GSH by the cornea in the young, adult guinea pigs is carrier mediated via mechanism (s) that can be dissociated from the transpeptidation pathway. The reduced availability of circulating GSH may be an important factor in the development of corneal pathology associated with aging and corneal hydration due to relative GSH deficiency.