GLUCOSE-METABOLISM IN CAT OUTER RETINA - EFFECTS OF LIGHT AND HYPEROXIA

Purpose. To determine the roles of oxidation and glycolysis with aerob ic and anaerobic lactate formation in the glucose metabolism of the ca t outer retina in light and darkness. Methods. Blood was collected fro m a choroidal vein and from an artery, and veno-arterial differences i n lactate concentration (Lac(v-a)) were determined at increasing light intensities. Blood also was sampled under conditions of darkness, lig ht, and hyperoxia and were analyzed for oxygen, glucose, and lactate c oncentrations with or without blood flow determinations. Results. When the dark-adapted eye was subjected to increasing light intensities, t here was a reduction in the Lac(v-a), indicating reduced glycolysis in the outer part of the retina as the rods saturated. In darkness, the mean lactate formation per retina was 0.409 mu mol/minute, oxygen cons umption was 0.198 mu mol/minute, and glucose consumption 0.236 mu mol/ minute. In light, the corresponding figures were 0.253, 0.166, and 0.1 23 mu mol/minute. Hyperoxia reduced lactate formation and increased ox ygen consumption in light and in darkness. Conclusions. Approximately 80% of the glucose consumed by the outer retina is used primarily in a erobic lactate formation. Because it is more efficient, oxidation of g lucose still accounts for most of the energy production in light and i n darkness. Light reduces oxidation as well as aerobic and anaerobic l actate formation.