CALCIUM GRADIENTS AND LIGHT-EVOKED CALCIUM CHANGES OUTSIDE RODS IN THE INTACT CAT RETINA
CALCIUM GRADIENTS AND LIGHT-EVOKED CALCIUM CHANGES OUTSIDE RODS IN THE INTACT CAT RETINA
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DOI：
10.1017/s0952523800003059
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发表时间：
1994-07-01
影响因子：
1.9
通讯作者：
STEINBERG, RH
中科院分区：
文献类型：
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作者：
GALLEMORE, RP;LI, JD;STEINBERG, RH
我们使用离子敏感的双管微电极研究了完整猫眼中细胞外Ca2+浓度（[Ca2+](o)）的光诱发变化。在视网膜位置的不同，观察到Ca2+浓度的两个显著变化。光诱发的[Ca2+]增加伴随着短暂的ON和OFF瞬态，其中在内丛状层最大，未作进一步研究。有一个意想不到的持续的光诱发的[Ca2+](o)下降，相对快速的开始和抵消，这是最大的视网膜下空间（SRS）的远端区域。在黑暗适应期间，SRS中的[Ca2+](o)比玻璃体中的高1.0 mM，这种跨视网膜梯度在杆饱和照明下消失。在校正了光诱发的SRS体积的增加后，揭示了照明期间SRS总Ca2+含量的增加，这可能代表了杆状体释放的Ca2+。为了解释光诱发的[Ca2+](o)变化，我们使用了随附论文（Li et al., 1994b）中描述的扩散模型，并在视网膜/视网膜色素上皮（RPE）边界和杆外段添加了依赖光的Ca2+来源。我们得出的结论是，光感受器周围的[Ca2+](o)下降，在照明期间持续存在并降低视网膜上Ca2+梯度，是光诱发的SRS体积增加，光感受器Ca2+释放和未知机制(s)的综合作用，这可能是RPE的Ca2+运输。[Ca2+](o)减少的相对快速的开始和抵消仍然无法解释。[Ca2+](o)的这些稳态变化应该对光感受器功能，特别是适应有显著影响。
We have studied light-evoked changes in extracellular Ca2+ concentration ([Ca2+](o)) in the intact cat eye using ion-sensitive double-barreled microelectrodes. Two prominent changes in Ca2+ concentration were observed that differed in retinal location. There was a light-evoked increase in [Ca2+],, accompanied by brief ON and OFF transients, which was maximal in the inner plexiform layer and was not further studied. There was an unexpected sustained light-evoked decrease in [Ca2+](o), of relatively rapid onset and offset, which was maximal in the distalmost region of the subretinal space (SRS). [Ca2+](o) in the SRS was 1.0 mM higher than in the vitreous humor during dark adaptation and this transretinal gradient disappeared during rod-saturating illumination. After correcting for the light-evoked increase in the volume of the SRS, an increase in the total Ca2+ content of the SRS during illumination was revealed, which presumably represents the Ca2+ released by rods. To explain the light-evoked [Ca2+](o) changes, we used the diffusion model described in the accompanying paper (Li et al., 1994b), with the addition of light-dependent sources of Ca2+ at the retina/retinal pigment epithelium (RPE) border and rod outer segments. We conclude that a drop in [Ca2+](o) around photoreceptors, which persists during illumination and reduces a transretinal Ca2+ gradient, is the combined effect of the light-evoked SRS volume increase, Ca2+ release from photoreceptors, and an unidentified mechanism(s), which is presumably Ca2+ transport by the RPE. The relatively rapid onset and offset of the [Ca2+](o) decrease remains unexplained. These steady-state shifts in [Ca2+](o) should have significant effects on photoreceptor function, especially adaptation.