Abnormal orotic acid metabolism associated with acute hyperammonaemia in the rat.
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Incorporation of uracil and uridine into ribonucleic acid (RNA) was compared among the ascitic and solid forms of Ehrlich mouse tumor, Morris hepatoma, Rhodamine sarcoma, gastric cancer and ulcer from human patients, and several normal rat tissues. Of these cells tested, the cells of Ehrlich ascites and solid tumors, human gastric cancer and ulcer, and certain tissues of a normal rat showed a considerably high activity. Furthermore, Ehrlich ascites tumor cells indicating a high incorporation activity was also high in activities of both phosphorylase and kinase for uridine, while Rhodamine sarcoma as a representative having a low incorporation activity was considerably low in these two enzymic activities. RNA synthesis from uridine phosphates by Rhodamine sarcoma was maintained to a fairly high extent contrary to its low activities of the phosphorylase and the kinase. Consequently, the low utilization of uracil and uridine by certain tumors was suggested to be due to the extremely low activities of both enzymes.
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Arginine deficiency is known to lead to marked alterations in pyrimidine biosynthesis and the excessive loss of urinary orotic acid. Orotic acid feeding is known to lead to hepatic steatosis. These studies show that arginine deficiency also results in a marked increase in liver lipids in the rat. The majority of the increased liver lipid can be accounted for by triglyceride accumulation. Increased liver lipid infiltration was found to be independent of the sex of the rat. Accompanying this increase was a decrease in serum triglycerides and cholesterol concentrations. Fatty infiltrations induced by arginine deficiency could be reversed by refeeding an arginine enriched diet. Adenine supplementation (0.30%) to the arginine deficient diet also completely prevented the induction of fatty livers. Adenine supplementation resulted in a dramatic increase in urinary orotic acid excretion in the arginine deficient rat. Guanine supplementation (0.5%) to an arginine deficient diet reduced but did not prevent the induction of fatty livers. The similarities of fatty livers induced by arginine deficiency and orotic acid feeding are discussed.
Thymine and cytosine as well as the intermediates in pyrimidine biosynthetic pathway dihydroorotic acid, orotic acid, carbamyl aspartate and 5'-uridine monophosphate and folic acid, was synergistic. 2-14C-Thymine, 6-14C-orotic acid and 14C-formate but not 2-14C-uracil, were incorporated into DNA more in the presence of aflatoxin. These findings indicated that aflatoxin inhibited the pyrimidine base synthesis which could be overcome to a great extent by the addition of thymine and folic acid to aflatoxin-treated cells.
Young healthy volunteers received a purine-free, isoenergetic formula diet over a period of 28 to 32 days. After a short time under formula diet alone 400 mg allopurinol were administered daily. After a further 10 days each volunteer received daily, in addition, either 4 g RNA, 4 g RNA-hydrolysate, 1 g guanosine-5-monophosphate (GMP), 1 or 3 g adenosine-5-monophosphate (AMP), uridine-5-monophosphate (UMP), cytidine-5-monophosphate (CMP) or adenosine, guanosine, uridine, cytidine, guanine, hypoxanthine, xanthine, cytosine and uracil. Finally the allopurinol was omitted. The renal excretion of total orotic acid (orotic acid and orotidine), uric acid and creatinine was determined daily; serum uric acid concentrations and the enzyme activities of orotidine-5-phosphate-decarboxylase (ODCase) and hypoxanthine-guanine-phosphoribosyltransferase (HGPRTase) from erythrocytes were determined every other day. The results show that RNA, RNA-hydrolysate, purine- and pyrimidine-nucleotides and -nucleotides as well as hypoxanthine, and to a lesser extent adenine, diminish allopurinol-induced orotaciduria. This is compatible with an influence of dietary purines and pyrimidines on human pyrimidine biosynthesis.
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Twenty amino acids were examined for their effects on urinary orotic acid excretion. Except for arginine and ornithine, all of the remaining amino acids tested induced a mild orotic aciduria in rats 2 hours post feeding. Two ammonium salts, and urease also acted, as inducers of orotic aciduria. The ammoneogenic properties of the amino acids tested could not solely explain the induced excretion of orotic acid. Only serine, glutamine, NH4Cl, (NH4)2CO3, and urease increased orotic acid excretion in the 24 hour fasted rat. Administration of 0.5 mmoles of arginine or ornithine ameliorated the mild orotic aciduria induced by either glycine or lysine. Arginine was shown to be more efficacious in preventing glycine induced orotic aciduria than was ornithine. Amino acid induced orotic aciduria is dependent upon the physiological state of the animal, varying with the state of digestion and the supply of arginine.
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The process of carcinogenesis following exposure of mice to urethane is demonstrated in the present work to be intimately related to nucleic acid synthesis. Injection of animals with a DNA hydrolysate immediately prior to a single exposure of the animals to urethane markedly reduced the number of pulmonary adenomas initiated. Aminopterin, known to interfere in nucleic acid synthesis (46), potentiated the carcinogenic action of urethane and this potentiation was blocked by injection of a DNA hydrolysate. Of the components and precursors of nucleic acids the pyrimidine series seemed especially concerned. Alterations in the utilization of oxaloacetate, ureidosuccinic acid, dihydro-orotic acid, orotic acid, cytidylic acid, and thymine appeared to be critical steps in the oncogenic process, following upon the primary disorder of cellular metabolism initiated by the carcinogen. All these substances except oxaloacetate profoundly reduced the number of tumors initiated by urethane. Oxaloacetate potentiated the carcinogenic effect. When these results are viewed together and in relation to known facts concerning nucleic acid synthesis they provide evidence suggesting that the point of action of the carcinogen is in the pathway of nucleic acid synthesis below orotic acid and perhaps at the level of ureidosuccinic acid. The potentiating influence of adenine, 4-amino-5-imidazole carboxamide, and aminopterin, the lack of effect of uracil, and the inhibitory influence of thymine together suggest that DNA rather than RNA is the nucleic acid critical to the oncogenic response of mice to urethane.
OBJECTIVES: To set up a novel simple, sensitive, and reliable ion-pairing HPLC method for the synchronous separation of several purines, pyrimidines, N-acetylated amino acids, and dicarboxylic acids for the chemical diagnosis and screening of inborn errors of metabolism (IEM). DESIGN AND METHODS: The separation was set up using a Hypersil C-18, 5-microm particle size, 250 x 4.6 mm column, and a step gradient using two buffers and tetrabutylammonium hydroxide as the pairing reagent. A highly sensitive diode array UV detector was set up at a wavelength between 200 and 300 nm that revealed purines and pyrimidines at 260 nm and other compounds at 206 nm. RESULTS: Compounds were determined in the plasma of 15 healthy adults, in the urine of 50 healthy subjects (1-3 years, 4-6 years, 8-10 years, 12-18 years, 25-35 years), and in 10 non-pathological amniotic fluid samples. To assess the validity of the chemical diagnosis of IEM, plasma and urine samples were analyzed in patients affected by Canavan disease (n = 10; mean age 4.6 +/- 2.3). Low plasma levels of N-acetylaspartate (16.96 +/- 19.57 micromol/L plasma; not detectable in healthy adults) and dramatically high urinary N-acetylaspartate concentrations (1872.03 +/- 631.86 micromol/mmol creatinine; 450 times higher than that which was observed in age-matched controls) were recorded. Neither N-acetylglutamate nor N-acetylaspartylglutamate could be detected in the plasma or urine of controls or patients with Canavan disease. CONCLUSIONS: The results demonstrate the suitability of the present ion-pairing HPLC separation with UV detection of cytosine, cytidine, creatinine, uracil, uridine, beta-pseudouridine, adenine, 3-methyladenine, hypoxanthine, xanthine, xanthosine, inosine, guanosine, ascorbic acid, thymine, thymidine, uric acid, 1-methyluric acid, orotic acid, N-acetylaspartate, N-acetylglutamate, N-acetylaspartylglutamate, malonic acid, methylmalonic acid, GSH, and GSSG as a reliable method for the prenatal and neonatal chemical diagnosis and screening of IEM using biological fluids.
The effect of several derivatives of ureidosuccinic acid on the growth of Escherichia coli 387, Staphylococcus aureus strain 209 and its mutant UV-2, Sarcina lutea, Candida tropicalis and Neurospora crossa 9863 as pre-screening systems for antitumor activity was studied. It was found that dihydrazide of D,L-ureidosuccinic acid (DHUA) had a marked antibacterial activity. The inhibitory effect of DHUA on N. crassa could not be removed by aspartic acid, ureidosuccinic acid, dihydroorotic acid, orotic acid, uracil or cytosine. DHUA suppressed the growth of Myeloma P-8 by 38%, that of Sarcoma 180 by 12% and that of Yoshida sarcoma by 19%. No effect was found on the growth of Lymphosarcoma Pliss.