vitamin-b-12 and purine

Topics: Anemia, Megaloblastic; DNA; Folic Acid; Gastrointestinal Absorption; Humans; Purines; Pyrimidines; Thymine Nucleotides; Vitamin B 12; Vitamin B 12 Deficiency

Topics: 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; Anemia, Megaloblastic; Animals; Central Nervous System; Deoxyuridine; Disease Models, Animal; Drug Interactions; Enzyme Activation; Folic Acid; Folic Acid Deficiency; Histidine; Humans; Liver; Methionine; Methylmalonyl-CoA Mutase; Nitrous Oxide; Oxidation-Reduction; Pteroylpolyglutamic Acids; Purines; Serine; Tetrahydrofolates; Thymidylate Synthase; Vitamin B 12; Vitamin B 12 Deficiency

To determine if folinic acid supplementation during methotrexate (MTX) therapy for rheumatoid arthritis (RA) reduces both urinary 5-aminoimidazole-4-carboxamide (AICA) and urinary adenosine excretion more than does folic acid supplementation. AICA and adenosine are markers for MTX interference with purine metabolism.. Forty patients with RA who received MTX for 6 weeks were randomized to receive either daily folic acid or folinic acid supplements during an additional week of MTX therapy. Colorimetric and radioimmunocompetition assays were used to measure 24-hour urinary AICA and adenosine excretion levels, respectively.. At the end of 6 weeks, 24-hour urinary levels of AICA, but not adenosine, were elevated as compared with baseline levels (i.e., prior to MTX therapy). Folinic acid, but not folic acid, supplementation normalized urinary AICA levels during MTX therapy. Relatively high urinary levels of AICA were correlated with reduced disease activity. No similar correlations were seen with urinary adenosine levels.. The blockade of purine nucleotide biosynthesis by MTX at the AICA ribonucleotide transformylase-catalyzed step may be related to the efficacy of MTX, and this blockade is effectively relieved by folinic acid, but not by folic acid, supplementation.

Topics: Adenosine; Aminoimidazole Carboxamide; Arthritis, Rheumatoid; Erythrocytes; Female; Folic Acid; Homocysteine; Humans; Leucovorin; Male; Methotrexate; Middle Aged; Purines; Pyridoxine; Ribonucleotides; Treatment Outcome; Vitamin B 12

The activity of the two folate dependent enzymes supplying carbon 2 and carbon 8 of the purine nucleus was assayed in the bone marrow of rats and man, as well as in rat livers. The activity of both enzymes was several fold greater in marrow than in liver. Inactivation of cobalamin by exposure to nitrous oxide did not affect the enzymes in rat marrow cells, although an appreciable effect on hepatic enzymes was found. The depression of hepatic glycinamide ribotide (GAR) transformylase in rats exposed to nitrous oxide was prevented by supplying a formate precursor, methylthioadenosine. There was a considerable rise in the activity of GAR transformylase in human marrow cells from patients with megaloblastic anaemia due to cobalamin deficiency but no change in activity in marrow from patients deficient in folate.

Topics: Acyltransferases; Adenosine; Anemia, Megaloblastic; Animals; Bone Marrow; Deoxyadenosines; Humans; Hydroxymethyl and Formyl Transferases; Liver; Male; Methionine; Nitrous Oxide; Phosphoribosylaminoimidazolecarboxamide Formyltransferase; Phosphoribosylglycinamide Formyltransferase; Purines; Rats; Rats, Inbred Strains; Thionucleosides; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Adenine; Cobamides; Corrinoids; Nitrous Oxide; Nucleosides; Purines; Research; Vitamin B 12

Topics: Alkalies; Benzimidazoles; Corrinoids; Hematinics; Purines; Vitamin B 12

Topics: Corrinoids; DNA; DNA, Bacterial; Glycine; Lactobacillus; Lactobacillus leichmannii; Purines; RNA; RNA, Bacterial; Vitamin B 12; Vitamins

Topics: Animals; Bone Marrow; Carbon Isotopes; DNA; Liver; Metabolism; Oxidoreductases; Physiology; Poultry; Purines; Research; Thymine; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Biochemical Phenomena; Lactobacillus; Lactobacillus leichmannii; Metabolic Networks and Pathways; Purines; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Biochemistry; Cobamides; Coenzymes; Purines; Vitamin B 12

Topics: Corrinoids; Guanine; Purine Nucleosides; Purines; Sewage; Vitamin B 12

Topics: Bone Marrow; Corrinoids; Folic Acid; Hematinics; Humans; Liver Extracts; Nucleotides; Purines; Vitamin B 12

Topics: Hematinics; Purines; Vitamin B 12

Topics: Adenine; Humans; Purines; Vitamin B 12; Vitamins; Xanthines

Topics: Corrinoids; Humans; Lactobacillus; Lactobacillus leichmannii; Metabolic Networks and Pathways; Purines; Pyrimidines; Thymidine; Vitamin B 12

Topics: Corrinoids; Purines; Vitamin B 12