Figure 6. NMR signals of brain extracts without contamination from blood.
13C NMR spectra show the signals from lactate and/or 2,3-bisphosphoglycerate in the perchloric acid extracts of blood and brain from a rat receiving [2,3-13C2]glucose. 2,3-bisphosphoglycerate is a unique metabolite in erythrocytes. In blood extracts of this animal, the signal from 2,3-bisphosphoglycerate is 4-fold of that from lactate. The absence of 2,3-bisphosphoglycerate signal of the brain extracts demonstrates minimal contamination by blood. Thus 13C-labeling pattern of lactate in the brain extracts essentially reflects brain metabolism only. Similar observations were made in other organ tissues.