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

The [14C]2-deoxyglucose (2-DG) technique has been widely utilized for quantitative measurement of local cerebral metabolic 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 audioradiographic 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 micrometer. 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 muCi/100 g) and 5 rats received [14C]2-DG (7.5 muCi/100 g). The mean 1CMRG values for selected areas of the central nervous system demonstrated no significant difference (P greater than 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).