Extracellular glucose dependence of rhodopsin regeneration in the excised mouse eye

To study the process of rhodopsin regeneration a superfused excised whole eye preparation of the albino mouse was developed. With this preparation, complete regeneration could be observed after each of the first two illuminations (bleaching 15-20%), and incomplete regeneration after a third illumination. Regeneration was minimal at extracellular glucose concentrations of 0 or 1 mM with improved regenerations at higher concentrations. Maximum regenerations were observed at glucose concentrations of 4-10 mM. First-bleach regenerations were as follows: 0 mM glucose, 20%; 1 mM, 8%; 2 mM, 45%; 3 mM, 82%; 4 mM, 115%; 5.1 mM, 121%; 7 mM, 120%; and 10 mM, 126%. The effects of reduced glucose were reversible. After an initial bleach with 0 or 1 mM extracellular glucose that exhibited minimal regeneration, the re-addition of glucose (5.1 mM) restored the ability of the eye to regenerate rhodopsin following a second bleach, but only to the level prior to that bleach. Mitochondrial substrates fumarate (10 mM) or pyruvate (10 mM) partly substituted for glucose, exhibiting first-bleach regenerations of 56 and 85%, respectively.