Metabolic dependence of photoreceptors on the choroid in the normal and detached retina.
Metabolic dependence of photoreceptors on the choroid in the normal and detached retina.
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DOI：
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发表时间：
2000-09
影响因子：
4.4
通讯作者：
R. Linsenmeier;L. Padnick-Silver
中科院分区：
文献类型：
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作者：
R. Linsenmeier;L. Padnick-Silver
目的本文评估了与脉络膜循环相关的高血流量和低 O(2) 提取在代谢上是必要的假设，并探讨了脉络膜和光感受器之间的空间关系对正常和脱离视网膜中代谢的影响。方法 先前使用猫中的 O(2) 敏感微电极测量了视网膜层上的 O(2) 分布。将轮廓拟合到扩散模型以获得表征光感受器 O(2) 需求的参数。这是一项基于这些参数的模拟研究。结果 感光器内部节段具有较高的 O(2) 需求 (QO(2))，并且距脉络膜较远（20 至 30 微米）。这些不寻常的情况需要大量 O(2) 通量流向内节段，这反过来又需要高脉络膜氧张力 (PO(2))、高脉络膜静脉饱和度 (ScvO(2))、每单位体积血液的低脉络膜 O(2) 氧提取量以及至少 500 ml/100 g-min 的脉络膜血流量 (ChBF)。视网膜脱离时发生的内部节段远离脉络膜的移动严重降低了内部节段获得O(2)的能力，即使对于小至100微米的脱离高度也是如此。根据脱离高度以及在吸入 O(2) 升高（高氧）期间对脉络膜和视网膜内部 PO(2) 的假设，高氧预计会在脱离期间部分或完全恢复光感受器 QO(2)。结论 脉络膜没有过度灌注，但需要高流速以满足视网膜的正常代谢需求。由于光感受器的氧合在正常情况下勉强充足，因此脱离会产生严重的代谢后果。预计高氧在脱离过程中具有临床益处。
PURPOSE This article assesses the hypothesis that the high blood flow rate and low O(2) extraction associated with the choroidal circulation are metabolically necessary and explores the implications of the spatial relationship between the choroid and the photoreceptors for metabolism in the normal and detached retina. METHODS The O(2) distribution across the retinal layers was previously measured with O(2)-sensitive microelectrodes in cat. Profiles were fitted to a diffusion model to obtain parameters characterizing photoreceptor O(2) demand. This was a study of simulations based on those parameters. RESULTS Photoreceptor inner segments have a high O(2) demand (QO(2)), and they are far (20 to 30 microm) from the choroid. These unusual conditions require a large O(2) flux to the inner segments, which in turn requires high choroidal oxygen tension (PO(2)), high choroidal venous saturation (ScvO(2)), low choroidal O(2) oxygen extraction per unit volume of blood, and a choroidal blood flow (ChBF) of at least 500 ml/100 g-min. Movement of the inner segments further from the choroid, which occurs in a retinal detachment, severely reduces the ability of the inner segments to obtain O(2), even for detachment heights as small as 100 microm. Depending on detachment height and assumptions about choroidal and inner retinal PO(2) during elevation of inspired O(2) (hyperoxia), hyperoxia is predicted to partially or fully restore photoreceptor QO(2) during a detachment. CONCLUSIONS The choroid is not overperfused, but requires a high flow rate to satisfy the normal metabolic demand of the retina. Because the oxygenation of the photoreceptors is barely adequate under normal conditions, detachment has serious metabolic consequences. Hyperoxia is predicted to have clinical benefit during detachment.