Glucose metabolism in pig outer retina in light and darkness

Glucose metabolism in the outer retina of pigs was studied in the light and in the dark in pentobarbital anaesthetized pigs. Blood was collected from a vortex vein and an artery, and the arteriovenous concentration differences of lactate, glucose and oxygen were determined in light-adapted eyes. Local blood flows were simultaneously determined using the microsphere method. In a second group of experiments, the flow from a vortex vein and arteriovenous concentration differences were measured in both darkness and light. In light, the mean net lactate formation and oxygen and glucose consumption in the outer retina were about 0.137, 0.150 and0.115 mumol min-1, respectively. In eyes previously dark-adapted, constant light caused a 63% reduction in lactate formation, whilst oxygen and glucose consumptions were reduced by 40 and 44%, respectively. The results indicate that in both darkness and constant light, most of the glucose consumed by the outer retina is used in lactate formation, and that less than 20% is oxidized. Energy production through glycolysis and glucose oxidation is approx. 42% lower in constant light than in darkness.