Augmentation of Oxygen Consumption of Rat Brain in vitro by Various Carbohydrate Intermediates

Summary (1) Citrate ion in a concentration of 0.0416 M enhanced oxygen consumption of rat, cat, dog, rabbit, guinea pig, and mouse brain slices and brei in dextrose and Krebs-Ringer phosphate buffer. Optimal concentration for dextrose was 0.0166 M. This effect was noted also in rat heart and kidney. (2) Of the 7 Krebs-cycle intermediates used as substrates individually, only lactate ion in Krebs-Ringer phosphate maintained respiration of rat brain better than did dextrose. (3) When the possibility of enhancement by substrates other than citrate was tested, no other ions reacted in this way in Krebs-Ringer phosphate. (4) Phosphate ion concentration played an important role; very different results were found in its absence. (5) The citrate ion enhanced the respiratory rate of rat brain not only in the presence of dextrose but also in the presence of lactate. (6) It is noteworthy that the respiratory rate of brain in vitro is affected in a unique fashion by citrate ion; that lactate is used by brain in the absence of dextrose more effectively than any other substance tested; and that phosphate ion influences the effects of various substrates.