Measurement of cerebral glucose utilization from brain uptake of [14C]2-deoxyglucose and [3H]3-O-methylglucose in the mouse

Abstract

Glucose utilization (GU) in the mouse brain in vivo was measured by the simultaneous use of [14C]2-deoxyglucose (2DG), the glucose analogue that can be phosphorylated in the brain, and [3H]3-O-methylglucose (3MG), the nonmetabolizable glucose analogue. Originally, this method was developed by Gjedde et al. (1985) in the rat and in humans. The present study examined the validity of this method in the mouse brain. The effects of urethane and pentobarbital (PB) on GU were also studied. Whereas the distribution volume of 3MG reached a constant value under each condition after 10 min of the tracer circulation, the apparent volume of distribution of 2DG, which increased with time in the awake mice, did not increase so greatly in the anesthetized and hypothermic mice, indicating that the net rate of 2DG phosphorylation is lowered under these conditions. These data were fitted for the conventional three-compartmental model and the values of rate constants of influx (K1), efflux (k2), phosphorylation, and dephosphorylation for 2DG, and K1 and k2 for 3MG were computed by nonlinear least square regression method. No significant difference in the value of K1/k2, the distribution volume of the precursor pool, was observed between 2DG and 3MG, indicating that 3MG can be used to estimate the distribution volume of unmetabolized 2DG in the brain. The values of GU calculated from the values of estimated parameters were not significantly different from those calculated from blood and tissue radioactivities obtained during 10 min after the injection of the tracers in both awake and PB-anesthetized mice. These findings indicate that the double tracer technique is useful for measuring GU in a short duration experiment.