How Does the Eye Breathe? EVIDENCE FOR NEUROGLOBIN-MEDIATED OXYGEN SUPPLY IN THE MAMMALIAN RETINA*

Visual performance of the vertebrate eye requires large amounts of oxygen, and thus the retina is one of the highest oxygen-consuming tissues of the body. Here we show that neuroglobin, a neuron-specific respiratory protein distantly related to hemoglobin and myoglobin, is present at high amounts in the mouse retina (100 M). The estimated concentration of neuroglobin in the retina is thus about 100-fold higher than in the brain and is in the same range as that of myoglobin in the muscle. Neuroglobin is expressed in all neurons of the retina but not in the retinal pigment epithelium. Neuro-globin mRNA was detected in the perikarya of the nu-clear and ganglion layers of the neuronal retina, whereas the protein was present mainly in the plexi-form layers and in the ellipsoid region of photorecepto