Light-induced pH changes in the intact retinae of normal and early diabetic rats.
Light-induced pH changes in the intact retinae of normal and early diabetic rats.
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DOI：
10.1016/j.exer.2015.11.015
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发表时间：
2016-04
影响因子：
3.4
通讯作者：
Linsenmeier RA
中科院分区：
文献类型：
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作者：
Dmitriev AV;Henderson D;Linsenmeier RA
用双管H+选择性微电极测定暗适应麻醉Long-Evans大鼠视网膜局部细胞外H+浓度([H+]o)。微电极以30μm的步长穿过视网膜，从玻璃体表面到视网膜色素上皮，再到脉络膜，记录光刺激引起的[H+]o的变化。糖尿病大鼠在腹腔注射链脲佐菌素1至3个月后进行记录，并将结果与年龄匹配的对照组动物的数据进行比较。短暂的光刺激(2.5 S)可引起[H+]o的变化，幅度仅为几nM。在整个视网膜，虽然这些成分的幅度和动力学在不同的视网膜层中略有不同，但在整个视网膜中，有大约200ms的短暂初始酸化，然后是稳定的碱化。早期糖尿病大鼠视网膜各层记录的光诱导的[H+]o变化与对照组动物相应层的[H+]o变化比较，差异无统计学意义。当H~+选择性微电极位于视网膜色素上皮(RPE)层时，可记录到H~+的增加，其时程和幅度与正常对照组和糖尿病大鼠相似。然而，在视网膜色素上皮基底膜远端的薄层(10-20μm)，正常对照组和糖尿病患者在脉络膜毛细血管内观察到显著不同的[H+]o变化。在对照组大鼠中，脉络膜[H+]o在少数情况下降低，但更多的情况下几乎没有变化。相比之下，糖尿病大鼠的脉络膜[H+]o要么增加(一半)，要么没有改变。这些数据表明，在糖尿病大鼠的早期阶段，脉络膜血供在稳定[H+]o方面的积极参与可能已经部分受损。有趣的是，糖尿病后1个月脉络膜循环的酸清除能力似乎受到最大影响，之后趋于改善。
Double-barreled H+-selective microelectrodes were used to measure local extracellular concentration of H+ ([H+]o) in the retina of dark-adapted anesthetized Long-Evans rats. The microelectrode advanced in steps of 30 μm throughout the retina from the vitreal surface to retinal pigment epithelium and then to the choroid, recording changes in [H+]o evoked by light stimulation. Recordings were performed in diabetic rats 1 to 3 months after intraperitoneal injection of streptozotocin and the results were compared with data obtained in age-matched control animals. Brief light stimulation (2.5 s) evoked changes of [H+]o with amplitudes of a few nM. Throughout the retina, there was a transient initial acidification for ~200 ms followed by steady alkalinization, although amplitudes and kinetics of these components were slightly variable in different retinal layers. No significant difference was found when the light-induced [H+]o changes recorded in various retinal layers of early diabetic rats were compared with the [H+]o changes from corresponding layers of control animals. Also, when H+-selective microelectrodes were located in the retinal pigment epithelium (RPE) layer, an increase in H+ was recorded, whose time course and amplitude were similar in control and diabetic rats. However, a striking difference between light-induced [H+]o changes in controls and diabetics was observed in the choriocapillaris, in the thin layer (10 – 20 μm) distal to the basal membrane of the RPE. In control rats, choroidal [H+]o decreased in a few cases, but much more often practically did not change. In contrast, diabetic rats demonstrated either an increase (in half of the cases) or no change in choroidal [H+]o. The data suggest that the active participation of the choroidal blood supply in stabilization of [H+]o could be partially compromised already at early stages of diabetes in rats. Interestingly, it appeared that the acid removal by the choroidal circulation was compromised most after 1 month of diabetes and tended to improve later.