Extracellular glucose dependence of rhodopsin regeneration in the excised mouse eye

Abstract

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 m m with improved regenerations at higher concentrations. Maximum regenerations were observed at glucose concentrations of 4–10 m m. First-bleach regenerations were as follows: 0 m m glucose, 20%; 1 m m, 8%; 2 m m, 45%; 3 m m, 82%; 4 m m, 115%; 5·1 m m, 121%; 7 m m, 120%; and 10 m m, 126%. The effects of reduced glucose were reversible. After an initial bleach with 0 or 1 m m extracellular glucose that exhibited minimal regeneration, the re-addition of glucose (5·1 m m) 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 m m) or pyruvate (10 m m) partly substituted for glucose, exhibiting first-bleach regenerations of 56 and 85%, respectively.