Carbon Balance Studies of Glucose Metabolism in Rat Cerebral Cortical Synaptosomes

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Abstract
Synaptosomes were isolated from rat cerebral cortex and incubated with [U-14C]-, [1-14C]- or [6-14C]glucose. Glucose utilization and the metabolic partitioning of glucose carbon in products were determined by isotopic methods. A carbon balance was constructed showing lactate to be the main product of glucose metabolism, followed by CO2, amino acids and pyruvate. Measuring the release of 14CO2 from glucose labeled in 3 different positions allowed the construction of a flow diagram of glucose C atoms in synaptosomes, which provides information about the contribution of the various pathways of glucose metabolism. Some 2% of glucose utilized was calculated to be degraded via the pentose phosphate pathway. Addition of chlorpromazine, imipramine or haloperidol at concentrations of 10-5 M reduced glucose utilization by 30% without changing the distribution pattern of radioactivity in the various products.