Aerobic glycolysis by the pituitary gland in vivo

Arteriovenous differences of glucose, lactate, and pyruvate were measured across the pituitary glands of overnight-fasted female pigs to determine whether net uptake of glucose occurred, and if so, whether it was oxidized or converted to lactate. Arteriovenous differences were also measured across a portion of the cerebral cortex as a control. Cerebral cortex oxidized 84% of the glucose taken up, but this was not true in the pituitary gland, where glucose was almost completely converted to lactate. The arteriovenous difference across the pituitary gland was 0.61 mumol/ml for glucose while the venoarterial differences of lactate and pyruvate were 1.0 and 0.07 mumol/ml, respectively. The results indicated that little net oxidation of glucose either by the Krebs cycle or the pentose phosphate pathway occurs in the pituitary gland in vivo. Estimates of the amount of energy released from aerobic glycolysis indicate that, unless the requirements of the neurohypophysis are very different from those in the rest of brain, very little energy could be derived from the metabolism of glucose.