Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3107, USA.
Exp Eye Res. 2012 Sep;102:50-8. doi: 10.1016/j.exer.2012.07.004. Epub 2012 Jul 22.
The purpose of this study was to investigate the oxygen distribution and consumption in the pigmented Long-Evans rat retina in vivo during dark and light adaptation, and to compare these results to previous work on cat and albino rat. Double-barreled microelectrodes recorded both intraretinal PO(2) depth profiles and the electroretinogram (ERG), which was used to identify the boundaries of the retina. Light adaptation decreased photoreceptor oxygen consumption per unit volume (Q(av)) from 3.0 ± 0.4 ml·100 g(-1) min(-1) (mean ± SEM) in darkness to 1.8 ± 0.2 ml·100 g(-1) min(-1) and increased minimum outer retinal PO(2) at the inner segments (P(min)) from 17.4 ± 3.0 to 29.9 ± 5.3 mmHg. The effects of light on outer retinal PO(2) and Q(av) were similar to those previously observed in cat, monkey, and albino rats; however, dark-adapted P(min) was higher in rat than cat. The parameters derived from fitting the oxygen diffusion model to the rat data were compared to those from cat. Oxygen consumption of the inner segments (Q(2)) and choroidal PO(2) (P(C)) in rat and cat were similar. P(min) was higher in rat than in cat for two reasons: first, rat photoreceptors have a shorter oxygen consuming region; and second, the retinal circulation supplied a greater fraction of consumed oxygen to rat photoreceptors. The average PO(2) across the inner retina (P(IR)) was not different in dark adaptation (25.4 ± 4.8 mmHg) and light adaptation (28.8 ± 5.4 mmHg) when measured from PO(2) profiles. However, with the microelectrode stationary at 9-18% retinal depth, a small consistent decrease in PO(2) occurred during illumination. Flickering light at 6 Hz decreased inner retinal PO(2) significantly more than an equivalent steady illumination, suggesting that changes in blood flow did not completely compensate for increased metabolism. This study comprehensively characterized rat retinal oxygenation in both light and dark, and determined the similarities and differences between rat and cat retinas.
本研究旨在研究活体色素性 Long-Evans 大鼠视网膜在暗适应和明适应过程中的氧分布和消耗情况，并将这些结果与先前关于猫和白化大鼠的研究进行比较。双腔微电极记录了视网膜内的局部氧分压（PO2）深度分布和视网膜电图（ERG），ERG 用于确定视网膜的边界。明适应使单位体积的光感受器耗氧量（Qav）从黑暗中的 3.0 ± 0.4 ml·100 g-1 min-1（平均值 ± SEM）降低到 1.8 ± 0.2 ml·100 g-1 min-1，并且增加了内节的最小外视网膜 PO2（Pmin）从 17.4 ± 3.0 到 29.9 ± 5.3 mmHg。光对外视网膜 PO2 和 Qav 的影响与先前在猫、猴子和白化大鼠中观察到的相似；然而，大鼠的暗适应 Pmin 高于猫。从大鼠数据拟合氧扩散模型得出的参数与猫的数据进行了比较。大鼠和猫的内节耗氧量（Q2）和脉络膜 PO2（P(C)）相似。大鼠的 Pmin 高于猫，原因有二：首先，大鼠的光感受器具有较短的耗氧区；其次，视网膜循环向大鼠的光感受器提供了更大比例的耗氧量。从 PO2 分布来看，暗适应时（25.4 ± 4.8 mmHg）和明适应时（28.8 ± 5.4 mmHg）内视网膜的平均 PO2（PIR）没有差异。然而，当微电极在 9-18%视网膜深度静止时，在照明过程中 PO2 会持续略有下降。6 Hz 的闪烁光会显著降低内视网膜 PO2，比等效的稳定光照降低得更多，这表明血流的变化并没有完全补偿代谢的增加。本研究全面描述了大鼠在明、暗适应条件下的视网膜氧合情况，并确定了大鼠和猫视网膜之间的相似性和差异。
