Country Michael W
Department of Biology, University of Ottawa, 30 Marie Curie Pvt., Ottawa, ON K1N 6N5, Canada.
Brain Res. 2017 Oct 1;1672:50-57. doi: 10.1016/j.brainres.2017.07.025. Epub 2017 Jul 29.
The retina is part of the central nervous system, and shares the characteristically high metabolism of the brain. The high energy demand of the retina is normally matched with a large supply of metabolites. When supply does not equal demand (e.g. if retinal blood flow is impaired), retinal neurons are at risk of excitotoxic cell death and vision is impaired or lost. Understanding the energetic budget of the retina is therefore crucial for understanding the pathology and treatment of retinal disease. In this minireview I give an overview of the energetics of the retina, with a focus on lessons learnt from comparative physiology. Retinas of all species studied thus far receive blood flow from choroidal capillaries. Additionally, fish, reptiles, and birds each have unique structures to increase metabolite supply. Primates and some mammals also have intra- and supraretinal vasculature to supply the retina, while other mammals rely solely on the choroid at the cost of retinal thickness. Neuroglobin, an oxygen-binding protein, may assist in oxygen delivery to counteract large diffusion distances from capillaries to mitochondria. Energy demand differs among models, as does mitochondrial location. More ATP is consumed in the dark due to Na/K ATPase activity to counteract the dark current, whereas phototransduction dominates ATP demand in the light. Photoreceptor metabolism is therefore especially high, and may be sustained with phosphocreatine and lactate shuttles. This comparative physiology approach raises new research questions, and suggests caution in comparing animal models of retinal disease, as they differ greatly in vasculature and energetics.
视网膜是中枢神经系统的一部分，具有与大脑相似的高代谢特征。视网膜对能量的高需求通常与大量代谢物供应相匹配。当供应与需求不相等时（例如视网膜血流受损），视网膜神经元有发生兴奋性毒性细胞死亡的风险，视力也会受损或丧失。因此，了解视网膜的能量收支对于理解视网膜疾病的病理和治疗至关重要。在这篇小型综述中，我概述了视网膜的能量学，重点是从比较生理学中获得的经验教训。迄今为止研究的所有物种的视网膜都接受脉络膜毛细血管的血流供应。此外，鱼类、爬行动物和鸟类各自具有独特的结构来增加代谢物供应。灵长类动物和一些哺乳动物还具有视网膜内和视网膜上血管系统来供应视网膜，而其他哺乳动物则仅依靠脉络膜，但以视网膜厚度为代价。神经球蛋白是一种氧结合蛋白，可能有助于氧气输送，以抵消从毛细血管到线粒体的较大扩散距离。不同模型的能量需求不同，线粒体的位置也不同。由于钠钾ATP酶的活性以抵消暗电流，在黑暗中消耗的ATP更多，而在光照下光转导主导ATP需求。因此，光感受器的代谢特别高，可能通过磷酸肌酸和乳酸穿梭来维持。这种比较生理学方法提出了新的研究问题，并建议在比较视网膜疾病的动物模型时要谨慎，因为它们在血管系统和能量学方面有很大差异。
