A comparison of the cerebral uptake and metabolism of labeled glucose and deoxyglucose in vivo in rats.

Experimental evidence indicated that: 1) [14C]deoxyglucose-6-phosphate (14C-DG-6-P) in brain (and other rat tissues) did not increase with time after injection of 14C-DG, 2) 14C-DG-6-P in rat brain (and other tissues) did not correlate with glucose metabolism, 3) 14C-DG-6-P in rat brain (and other tissues) had a significant negative correlation with glucose-6-phosphatase activity. Further, arterio-venous studies in rats, in which the cerebral uptake and metabolism of labeled glucose were compared directly with those of labeled DG (and labeled fluorodeoxyglucose, FDG), employing double labeled techniques, showed that DG (and FDG) cannot be used to measure glucose uptake and/or metabolism.