Purchase this article with an account.
Barry S. Winkler, Catherine A. Starnes, Brandon S. Twardy, Diane Brault, R. Craig Taylor; Nuclear Magnetic Resonance and Biochemical Measurements of Glucose Utilization in the Cone-Dominant Ground Squirrel Retina. Invest. Ophthalmol. Vis. Sci. 2008;49(10):4613-4619. doi: 10.1167/iovs.08-2004.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
purpose. To provide quantitative information on glucose utilization in cone-dominant ground squirrel retinas.
methods. Ground squirrel eyecups were incubated in medium containing 14C-glucose, and the production of 14CO2 was measured. Measurements were also made of lactic acid production (glycolysis). Nuclear magnetic resonance (NMR) was used to track metabolites generated from 13C-1 glucose.
results. Ground squirrel eyecups produced lactate at a high rate and exhibited normal histology. Light-adaptation reduced glycolysis by 20%. Ouabain decreased glycolysis by 25% and decreased 14CO2 production by 60%. Blockade of glutamate receptors had little effect on the glycolysis and 14CO2 produced. When metabolic responses were restricted to photoreceptors, light caused a 33% decrease in 14CO2 production. The rate of 14CO2 production was less than 10% of lactate production. Lactate was the major product formed from 13C-glucose. Other 13C-labeled compounds included glutamate, aspartate, glutamine, alanine, taurine, and GABA. Lactate was the only product detected in the medium bathing the ground squirrel retinas. The rod-dominant rat retina exhibited a similar pattern of metabolites formed from glucose.
conclusions. Lactate, not CO2, is the major product of glucose metabolism in both ground squirrel and rat retinas. Active Na+ transport, however, depends more on ATP produced by mitochondria than by glycolysis. A relatively high fraction of ATP production from glycolysis and glucose oxidation continues in the absence of active Na+ pumping and glutamatergic transmission. Major neurotransmitters are synthesized from the aerobic metabolism of glucose; anoxia-induced impairment in retinal synaptic transmission may be due to depletion of neurotransmitters.
This PDF is available to Subscribers Only