Metabolism of Glucose and Reduction of Retinaldehyde in Retinal Photoreceptors¹

Abstract —The capacity of a variety of substrates to support reduction of retinaldehyde to retinol by preparations of outer segments from photoreceptor cells of bovine retina, the requirement for supplements, the effect of iodoacetate, and the stoichiometry of the metabolism of glucose and the reduction of retinaldehyde have been studied. Metabolism of glucose supported reduction of retinaldehyde by preparations of outer segments at approximately the rate observed for the intact retina. Throughout the physiological range of pH, the dehydrogenase reactions of the pentose cycle in outer segments provided virtually all of the reduced pyridine nucleotides that were utilized for reduction of retinaldehyde. It was concluded that reduction of retinaldehyde during light adaptation is exclusively dependent upon NADPH.