caa a22 4500 386322724 CHVBK 20180307111632.0 cr unu---uuuuu 161130e198803 xx s 000 0 eng 10.1079/BJN19880035 doi S0007114588000364 pii (NATIONALLICENCE)cambridge-10.1079/BJN19880035 Utilization of tryptophan, nicotinamide and nicotinic acid as precursors for nicotinamide nucleotide synthesis in isolated rat liver cells [Elektronische Daten] 1. Incubation of isolated rat hepatocytes with nicotinamide or nicotinic acid showed that while both vitamers were taken up from the incubation medium, neither was utilized to any significant extent as a precursor of the nicotinamide nucleotide coenzymes, NAD and NADP, and neither was capable of preventing the loss of nucleotides that occurs on incubating the cells. 2. Incubation of hepatocytes with tryptophan showed that de novo synthesis from tryptophan permitted replacement of the nucleotides lost during incubation; at high concentrations of tryptophan there was an increase above the initial intracellular concentration of NAD(P). Incubation of hepatocytes with tryptophan also resulted in the formation and release from the cells of a considerable amount of niacin, as well as the two principal metabolities of NAD(P), N1-methyl nicotinamide and methyl pyridone carboxamide. 3. It is suggested that, in the liver, preformed niacin is not utilized for nucleotide synthesis, and indeed the function of the liver appears to be synthesis of niacin from tryptophan, and its release for use by extrahepatic tissues that lack the pathway for de novo synthesis of nicotinamide nucleotides from tryptophan. Copyright © The Nutrition Society 1988 Bender David A. Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WC1E 6BT Olufunwa Ronald Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WC1E 6BT British Journal of Nutrition Cambridge University Press 59/2(1988-03), 279-287 0007-1145 59:2<279 1988 59 BJN https://doi.org/10.1079/BJN19880035 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1079/BJN19880035 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Bender David A. Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WC1E 6BT NATIONALLICENCE 700 1- Olufunwa Ronald Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WC1E 6BT NATIONALLICENCE 773 0- British Journal of Nutrition Cambridge University Press 59/2(1988-03), 279-287 0007-1145 59:2<279 1988 59 BJN CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge