Glucose metabolism in cat outer retina. Effects of light and hyperoxia

To determine the roles of oxidation and glycolysis with aerobic and anaerobic lactate formation in the glucose metabolism of the cat outer retina in light and darkness.

Blood was collected from a choroidal vein and from an artery, and veno-arterial differences in lactate concentration (Lac(v-a) were determined at increasing light intensities. Blood also was sampled under conditions of darkness, light, and hyperoxia and were analyzed for oxygen, glucose, and lactate concentrations with or without blood flow determinations.

When the dark-adapted eye was subjected to increasing light intensities, there 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 mumol/minute, oxygen consumption was 0.198 mumol/minute, and glucose consumption 0.236 mumol/minute. In light, the corresponding figures were 0.253, 0.166, and 0.123 mumol/minute. Hyperoxia reduced lactate formation and increased oxygen consumption in light and in darkness.

Approximately 80% of the glucose consumed by the outer retina is used primarily in aerobic lactate formation. Because it is more efficient, oxidation of glucose still accounts for most of the energy production in light and in darkness. Light reduces oxidation as well as aerobic and anaerobic lactate formation.