CHANGES WITH AGE IN THE UTILIZATION OF GLUCOSE CARBON IN LIVER AND BRAIN

THE METABOLISM of the brain is characterized by a high rate of incorporation of glucose carbon into the free amino acids. The brain differs in this respect from other organs examined (ROBERTS, FLEXNER and FLEXNER, 1959; BUSCH, FUJIWARA and KEER, 1960; VRBA, GAITONDE and RICHTER, 1962; GAITONDE, DAHL and ELLIOTT, 1965). At 22 min after subcutaneous injection of uniformly labelled [14C]glucose in the cat, more than 70 per cent of the total 14C in the brain was found in the amino acids, whereas only 8-16 per cent of the 14C had entered the amino acids in liver, kidney, lung, muscle or spleen (GAITONDE, MARCHI and RICHTER, 1964). The work hitherto reported on the entry of glucose carbon into amino acids was carried out on adult animals or on animals in which the brain was functionally mature. This raises the question: does the rapid incorporation of glucose carbon into amino acids occur also in the immature brain, or at what age does this characteristic of brain metabolism appear ? The following experiments were undertaken to answer this question.