Reexamination of Glucose-6-Phosphatase Activity in the Brain in Vivo: No Evidence for a Futile Cycle

Abstract
Glucose-6-phosphatase activity in the rat brain in vivo was estimated by measuring the differential loss of tritium and carbon-14 from the glucose pool labeled by a mixture of [2- 3 H]glucose and [U- 14 C]glucose. The results provide no evidence of significant dephosphorylation of glucose-6-phosphate and do not support the hypothesis of a futile cycle involving glucose-6-phosphatase activity in the brain.