Significant dephosphorylation of glucose 6-phosphate due to glucose-6-phosphatase activity in rat brain in vivo was recently reported (Huang, M., and Veech, R. L. (1982) J. Biol. Chem. 257, 1135811363). The evidence was an apparent more rapid 3H than 14C loss from the glucose pool and faster [2-3H] glucose than [U-14C]glucose utilization following pulse labeling of the brain with [2-3H,U-14C]gl...