Urinary purines and pyrimidines in patients with hyperammonemia of various origins.

Excretion patterns of pyrimidines and purines in patients with various types of hyperammonemia have been investigated by 2-dimensional thin-layer chromatography and high pressure liquid chromatography (HPLC). For the quantitative analysis of pseudouridine, uracil and uridine a new procedure has been developed, consisting of pre-fractionation with Dowex 1 X 8, followed by dual column HPLC on a strong anion-exchanger and a reverse phase column. Thymine has also been analyzed in the pre-fractionated urine by a new HPLC method using the reverse phase column in combination with a strong cation-exchange column. Quantitative data for urinary pyrimidines and uric acid in hyperammonemia are given. In patients with a defect in one of the urea cycle enzymes, the level of pyrimidine excretion was found to depend on plasma ammonia concentrations. In other hyperammonemic patients, an increased excretion of orotic acid, uracil and uridine has only been found in one of the two patients with lysinuric protein intolerance, all other patients showing normal excretion patterns. Elevated uric acid excretions have been found frequently in our patients with hyperammonemia, but they did not always coincide with high plasma ammonia levels. A possible explanation for the difference in the excretion levels of the various pyrimidines is discussed.

Urinary excretion of methylated purines in man and in the rat after the administration of theophylline.

Chromatographic characteristics of urinary metabolites of theophylline were studied by two-dimensional thin-layer chromatography, high-performance liquid chromatography and gas chromatography--mass spectrometry. Quantitative date for the urinary metabolites of theophylline in asthmatic children are given. It was shown that 1,3-dimethyluric acid is the predominant excretory product. In addition, smaller amounts of 1-methyluric acid, 3-methylxanthine and unchanged theophylline were found. Excretory patterns after theophylline ingestion before and during the administration of allopurinol in asthma patients and in rats suggest the existence of three metabolic pathways of theophylline. The administration of this drug to a patient with xanthine oxidase of theophylline. The administration of this drug to a patient with xanthine oxidase deficiency resulted in the excretion of 1-methyluric acid in addition to 1,3-dimethyluric acid, 3-methylxanthine, 1-methylxanthine and unchanged theophylline. It was concluded that in man the oxidation of theophylline is not catalysed by xanthine oxidase.

Urinary excretion of orotic acid, orotidine and other pyrimidines in a patient with purine nucleoside phosphorylase deficiency.

Urinary orotidine and orotic acid have been determined in a patient with purine nucleoside phosphorylase (PNP) deficiency under various dietary therapeutic conditions. For this purpose a new procedure for the analysis of both compounds has been developed, consisting of prefractionation with Dowex 1X8, followed by two HPLC steps on a micro Bondapak NH2 and a micro Bondapak C18 column. With this method normal as well as slightly elevated excretions of orotic acid have been found in our patient. No evidence was obtained for inhibition of OPRT by purine (deoxy)nucleosides as a cause of pyrimidine starvation. A significant increase of urinary orotidine was found after loading with allopurinol. For comparison excretory values in a patient with ornithine transcarbamylase deficiency and also in a patient with orotic aciduria type I are shown. The possible cause of the slight increase in urinary orotic acid in our patient has been discussed.