The Deoxyglucose Method in the Ferret Brain. I. Methodological Considerations

In the brain of the anesthetized ferret, the 2-deoxyglucose (2-DG) transfer rate constants required to determine cerebral glucose utilization by the deoxyglucose method were calculated from regional gray matter time-radioactivity curves measured for 180 min after tracer injection. Results suggest that loss of metabolized tracer from brain occurs at a rate of about 1%/min for the first 180 min after injection if the rate constant of the rate-limiting step for loss of metabolized tracer ( k* 4 ) represents a first-order kinetic process. A simulation experiment shows that, whether k* 4 is assumed to be 0 or 0.01 min −1 , has a negligible influence on glucose utilization rates obtained in conventional 45 min autoradiographic experiments provided that the entire analysis, including lumped constant determination, is carried out in a consistent way. The 2-DG lumped constant for k* 4 = 0 is 0.54, and 0.68 for k* 4 = 0.01 min −1 .