The utilization of glucose in the brain and other organs of the cat

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Abstract
After subcutaneous injection of [14C]glucose in the cat the total14C content per gram fresh tissue was relatively high in liver, kidney, blood and brain: lower values were obtained in heart, spleen, lung, skeletal mucle and spinal cord. In all organs examined more than 95 % of the radioactivity present at 22 min after injection was contained in the acid-soluble fraction of the tissue: proteins, lipids and nucleic acids together accounted for only 0.2 to 5 % of the radioactivity. In most organs the14C in the acid-soluble fraction was present mainly as [14C]glucose, but in nervous tissues a large part (48 to 74 %) of the14C was contained in the free amino acid fraction. The incorporation of14C from [14C]glucose into amino acids (counts min-1g fresh tissue-1)in vivowas highest in the cerebral cortex and decreased in the order cerebral cortex > cerebellum > pons and medulla > spinal cord: the incorporation into amino acids was several times greater in the brain than in other organs examined. Values obtained for the heart were intermediate between those for brain and other organs. About 80 % of the14C incorporated into amino acids of the cerebral cortex was combined in glutamic and aspartic acids. In liver, spleen, muscle, lung and blood the basic and neutral amino acids accounted for a relatively larger proportion of the radioactivity of the amino acid fraction. The14C contained in tricarboxylic acid cycle intermediates accounted for 20 to 32 % of the radioactivity of the acid-soluble fraction in different parts of the brain.