ABSTRACT
The participation of glutamate and alanine in lipogenesis and gluconeogenesis of brain was investigated. 5(14)C glutamate was injected intracisternally in an amount of 5 mcCu/l g tissue and 3(14)C-alanine was injected subcutaneously 30 mcCu/100 g body weight. Labels from glutamate and alanine were recovered in different lipid franctions -- in phospholipids, glycerides, free fatty acids and cholesterol, as well as in glucose and glycogen. An intensive incorporation of label from 5(14)C glutamate into various amino acids--aspartic acid, glutamine, serine, glycine and alanine--was demonstrated. The data presented indicate the participation of amino acids in lipogenesis and gluconeogenesis of brain.
Subject(s)
Alanine/metabolism , Amino Acids/biosynthesis , Brain/metabolism , Gluconeogenesis , Glutamates/metabolism , Lipids/biosynthesis , Animals , Citrates/biosynthesis , Fatty Acids/biosynthesis , Ketoglutaric Acids/metabolism , RatsABSTRACT
The changes in the rates of citrate biosynthesis and utilization in rat brain, liver, kidney and heart, produced by hypoxia, action of 2,4-DNP and thyreotoxicosis, were compared with changes of some regulatory parameters under the same conditions. The comparison of citrate-synthase activities, citrate levels in tissues and 14C-incorporation from different precursors into citric acid permitted us to establish that the biosynthesis of citrate in brain was more intensive than in other tissues studied. The main source of acetyl-CoA for citrate-synthase reaction in brain is the oxidation of pyruvate. The ratio of adenine nucleotides plays an important role in the control of citrate-synthase activity in brain, where the oxaloacetate control is not as significant as in liver. NAD-specific isocitrate dehydrogenase reaction was found to be the dominant pathway for citrate oxidation in brain: more than 60 percent of brain citrate were oxidized by NAD-ICDH, while less than 10 percent of citric acid were utilized by this enzyme in other tissues studied. The existance of an adenine nucleotide control of NAD-ICDH activity in brain may be an additional mechanism for the regulation of the first steps of energy metabolism in brain.
Subject(s)
Brain/metabolism , Citrates/metabolism , Acetyl Coenzyme A/metabolism , Adenosine Triphosphate/pharmacology , Animals , Citrate (si)-Synthase/metabolism , Citrates/biosynthesis , Dinitrophenols/pharmacology , Hyperthyroidism/metabolism , Hypoxia, Brain/metabolism , Isocitrate Dehydrogenase , Isocitrates/metabolism , Kidney/metabolism , Liver/metabolism , Male , Mitochondria/metabolism , Myocardium/metabolism , NAD/pharmacology , NADP/pharmacology , Nitrites/pharmacology , RatsABSTRACT
The turnover rate of N-acetylneuraminic acid of brain gangliosides (GT1, GD1b, GD1a, GM1) was studied following the injection of 2-14C-acetate. The specific activity of N-acetylneuraminic acid in GD1a and GM1 was found to be higher than in GD1b. The administration of aminasine reduced the specific activity of N-acetylneuraminic acid whereas chlorhydrate increased that of major brain ganglosides.
Subject(s)
Brain/metabolism , Gangliosides/metabolism , Sialic Acids/metabolism , Animals , Chloral Hydrate/pharmacology , Chlorpromazine/pharmacology , RatsABSTRACT
The activities of NAD- and NADP-specific isocitrate dehydrogenases (ICDH) were investigated in subcellular fractions of rat brain and liver. Animals of different age groups were used: newborn, 10-, 20-, 30-, 40-days old and adult rats. It was shown that NAD-ICDH activity rose sharply in adult brain mitochondria as compared with that of developing animals. The NAD-dependent pathway of isocitrate oxidation predominated in mitochondria of both developing and adult brain. The activity of NADP-ICDH decreased in brain mitochondria and cytoplasm in the course of development. Some changes in the distribution of enzyme activity between subcellular fractions were also found in adult brain. The activity of mitochondrial NADP-ICDH was higher than that of newborn animals.
