Regional cerebral glucose utilization measured with [14C]glucose in brief experiments

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Abstract
A method was developed to measure regional cerebral glucose utilization (rCMRGlc) in very short times using autoradiography and [2- 14C]glucose. It includes a more comprehensive mathematical treatment than prototypes and allows greater experimental flexibility. The current model takes into account the exchange of glucose between plasma and brain as a function of the plasma glucose concentration and rCMRGlc. The loss of 14C as 14CO2, although relatively small, is also calculated and the results corrected accordingly. Fully metabolizable radiolabeled glucose was chosen as the tracer, because it most closely resembles the natural substrate. Glucose is more rapidly phosphorylated than analogues such as 2-deoxyglucose and the 14C accumulated within intermediary metabolites soon account for most of the radioactivity in cerebral tissue. Furthermore, no special constant is necessary to adjust the rates as is the case when analogues are used. Excellent anatomic resolution was achieved when the technique was used to determine rCMRGlc in experiments as short as 5 min. By taking this approach, more short-lived phenomena may be studied under more diverse conditions than was previously possible.