Quantitative measurement of local cerebral metabolic rate for glucose utilizing tritiated 2-deoxyglucose

Abstract

The [ 14C]2-deoxyglucose (2-DG) technique has been widely utilized for quantitative measurement of local cerebral metabolic rate for glucose (1CMRG) in animals. The technique as presently used is limited by the energy of 14C beta-particles, which can travel relatively great distances in tissue. This results in limited audiographic resolution and in computed 14C concentrations which are a function of tissue section thickness. [ 3H]2-DG has less energetic beta-particles; hence, autoradiographs have better resolution and optical densities are independent of tissue thickness for sections greater than 5 μm. We have developed a method for quantitation of 1CMRG in rats using [ 3H]2-DG and a newly developed ultrasensitive X-ray film. Autoradiographic tissue standards were prepared by injecting rats with [ 3H]2-DG and assaying micro-samples of brain for 3H concentration. Ten rats were used in this study. Five rats received [ 3H]2-DG (300 μCi/100 g) and 5 rats received [ 14C]2-DG (7.5 μCi/100g). The mean 1CMRG values for selected areas of the central nervous system demonstrated no significant difference ( P > 0.05) between the [ 14C]2-DG and the [ 3H]2-DG groups. Values for 1CMRG from the [ 3H]2-DG group showed no variation attributable to inadequate microtome precision. The improved resolution obtained by utilizing [ 3H]2-DG is especially evident where gray matter (high 1CMRG) is immediately adjacent to white matter (low 1CMRG).