Differential increase in cerebral cortical glucose oxidative metabolism during rat postnatal development is greater in vivo than in vitro

The steady-state rate of glucose oxidation through the mitochondrial TCA cy cle(V-TCA) was measured in acid extracts of 10- and 30-day-old cerebral cor tex of rats receiving [1-C-13]glucose intravenously and in neocortical slic es superfused in vitro with the same isotope. TCA cycle flux was determined for each age group based on metabolic modeling analysis of the isotopic tu rnover of cortical glutamate and lactate. The sensitivity of the calculated rates to assumed parameters in the model were also assessed. Between 10 an d 30 postnatal days, V-TCA increased by 4.3-fold (from 0.46 to 2.0 mu mol g (-1) min(-1)) in the cortex in vivo, whereas only a 2-fold (from 0.17 to 0. 34 mu mol g(-1) min(-1)) increase was observed in neocortical slices. The m uch greater increase in glucose oxidative metabolism of the cortex measured in vivo over that measured in vitro as the cortex matures suggests that fu nction-related energy demands increase during development, a process that i s deficient in the slice as a result of deafferentiation and other mechanis ms. (C) 2001 Elsevier Science B.V. All rights reserved.