RATES OF GLUCOSE-UTILIZATION IN BRAIN OF ACTIVE AND HIBERNATING GROUND-SQUIRRELS

Rates of glucose utilization (CMR(Glc)) were determined in some cerebr al structures of active warm- and cold-adapted ground squirrels and hi bernating ground squirrels with [C-14]deoxyglucose (DG) by direct chem ical measurement of precursor and products in samples dissected from f unnel-frozen brain. The rate of supply relative to demand of glucose a nd [C-14]DG in brain of hibernating animals was similar to or greater than that of controls. [C-14]DG cleared from the plasma in hibernators much more slowly than in active animals, and the level of unmetaboliz ed [C-14]DG in brain and the integrated specific activity of the precu rsor pool in plasma exceeded those of the active animals by 4- to 10-f old. At 45 min after an intravenous pulse of [C-14]DG, the unmetaboliz ed [C-14]DG remaining in the brains of the hibernators accounted for s imilar to 96% of the total C-14 compared with similar to 10-15% in the active animals. The value of lambda, a factor contained in the lumped constant of the operational equation of the [C-14]DG method, was esti mated for each animal and found to be relatively constant over the six fold range of glucose levels in the brains of all animals. Calculated CMR(Glc) in squirrels in deep hibernation was only 1-2% of the values in active animals.