Evaluation of radiolabeled acetate and fluoroacetate as potential tracers of cerebral oxidative metabolism.

We investigated the potential use of radiolabeled acetate (ACE) and fluoroacetate (FACE) as tracers of cerebral oxidative (Krebs cycle) metabolism. The rates of cerebral accumulation of 14C-labeled FACE and ACE were compared with glucose metabolic rates measured simultaneously with 18F-fluorodeoxyglucose (FDG) in awake rats using dual-tracer quantitative digital autoradiography. Both FACE and ACE crossed the blood-brain barrier at approximately the same rate as glucose. Metabolism of FACE by the brain, however, was extremely slow; metabolites were practically undetectable above background precursor levels through 60 min. Metabolic uptake of ACE by the brain was significant by 10 min; its rate of accumulation averaged approximately 70-80% of the glucose rate. While the metabolic images of ACE were similar to those of FDG, variations in the uptake patterns of FDG and ACE occurred in some structures, perhaps related to regional variations in glucose versus oxygen metabolism.