Hexose transport by brain slices: further studies on energy dependence

We studied the uptake of [3H]2-deoxyglucose [( 3H]2DG) by slices of rat cerebral cortex in vitro as a model of glucose transport by brain. Slices were incubated with [3H]2DG, or with L-[3H]glucose as a marker for diffusion; the difference between [3H]2DG uptake and L-[3H]glucose uptake was defined as net [3H]2DG transport. Net [3H]2DG transport was a function of incubation temperature, with an estimated temperature coefficient of 1.87 from 15 degrees C to 25 degrees C. The net uptake of [3H]2DG was not inhibited by phlorizin or phloretin in concentrations well above the reported Ki of these inhibitors for hexose uptake in other systems. To examine the hypothesis that [3H]2DG transport by brain slices is dependent on mitochondrial energy, we studied net [3H]2DG uptake by slices which had been preincubated in media designed to alter intracellular ATP stores. The transport process was very sensitive to inhibition by DNP, but the correlation between [3H]2DG transport and ATP levels was unclear. In contrast to our published hypothesis that the transport process required mitochondrial energy, these data indicate that dependence on energy is not absolute.