[Selective characterisation of N1-methyladenosine and N7-methylguanosine in urine (author's transl)]

We describe the selective analysis of N-methylated ribonucleosides, i.e., N1-methyl adenosine (m1Ado) and N7-methyl guanosine (m7Guo) in the presence of other nucleosides in urine. m1Ado as well as m7Guo were characterized by use of chromatographic techniques including substance specific chemical reactions.

Metabolic fate of N6-benzyladenosine and N6-benzyladenosine-5'-phosphate in rats

The radiolabeled antitumor nucleoside (14C-8)-N6-benzyladenosine and its (14C-8)-5'-phosphate were administered to rats intravenously, and their metabolic fate was studied. Twenty-nine percent of the radioactivity was recovered in the 48-hr urine collection after (14C-8)-N6-benzyladenosine administration. The following metabolites were isolated: unchanged N6-benzyladenosine (20%), adenine (12%), uric acid (5%), and N6-benzyladenine (0.3%). In the case of (14C-8)-N6-benzyladenosine-5'-phosphate, a total of 28% of the radioactivity was recovered in the 48-hr urine collection and the following metabolites were isolated: N6-benzyladenosine (40%), uric acid (12%), adenine (trace), and unidentified urea derivatives (30%). Metabolism of N6-benzyladenosine appears to involve N-debenzylation to some extent, followed by conversion to adenine and uric acid. N6-Benzyladenosine and its 5'-phosphate differ from other adenosine analogs in being retained in significant amounts by the animals.

Renal metabolism of N6,O2'-dibutyryl adenosine 3',5'-monophosphate

Metabolism of dibutyryl cyclic AMP was studied by including the 3H- or C-labeled nucleotide (0.1 mM, 5 mumol) in the recirculating perfusate of the isolated rat kidney. Kidneys were perfused with nucleotide for 60 min. Dibutyryl cyclic AMP was almost completely cleared from the perfusate, about one-quarter as urinary excretion principally by probenecid-sensitive secretion and about one-half as metabolism beyond 3'-phosphate bond cleavage. The principal metabolite, N6-monobutyryl adenosine, accounted for one-third of added dibutyryl cyclic AMP. The remaining metabolites were ATP, ADP AMP, and N6-monobutyryl AMP. Dibutyryl cyclic AMP (0.1 or 1.0 mM) elevated renal ATP but did not alter uricogenesis. Both dibutyryl cyclic AMP and cyclic AMP at 0.2 mM produced similar activation and subcellular redistribution of renal protein kinase. N6-monobutyryl adenosine, unlike adenosine, had no effect on the renal activity of adenylate cyclase, low Km cyclic AMP phosphodiesterase, and protein kinase. Dibutyryl cyclic AMP is like exogenous cyclic AMP in that it penetrates the rat kidney, activates protein kinase, and is metabolized to ATP (R. Coulson, J. Biol. Chem. 251: 4958-4967, 1976), but is unlike cyclic AMP in its extent of secretion and metabolism to ATP and urate and in its formation of the unique metabolites N6-monobutyryl AMP and N6-monobutyryl adenosine.

Overproduction of adenine deoxynucleosides and deoxynucletides in adenosine deaminase deficiency with severe combined immunodeficiency disease

The deoxynucleotide, dATP, is elevated 50- to 1,000-fold above normal in erythrocytes, lymphocytes, and bone marrow from a child with adenosine deaminase deficiency and severe combined immunodeficiency disease. The child, when 17 mo of age, was also excreting approximately 30 mg of deoxyadenosine per day in urine (normal is less than 0.1 mg/day). Urinary excretion of uric acid was decreased. Elevated dATP levels in lymphocytes and bone marrow, and increased urinary excretion of deoxyadenosine, persisted despite hypertransfusion of the child with irradiated erythrocytes from a donor with normal adenosine deaminase. Overproduction of deoxynucleotides by increased salvage of adenosine appears to be the primary metabolic abnormality in patients with adenosine de aminase deficiency.

Adenosine production in the ischemic kidney

We conducted experiments to determine (1) tissue, blood, and urine levels of adenosine produced by the ischemic kidney under conditions of renal artery occlusion, and (2) the site(s) of production and release of adenosine by the kidney. Concentrations of adenosine, inosine, and hypoxanthine in the dog urine were found to increase after 2 minutes of renal artery occlusion as were concentrations of these metabolites in renal tissue after 10 minutes of renal artery occlusion. Renal venous plasma levels of inosine and hypoxanthine also were elevated after 3 minutes of arterial occlusion. In modified stop-flow experiments, adenosine appeared in the urine in a peak that corresponded most closely with proximal tubule fluid. 5'-Nucleotidase, the enzyme which catalyzes the dephosphorylation of 5'-AMP or 5'-IMP to adenosine or inosine, respectively, was found to be located primarily on the external membranes and mitochondria of proximal tubule cells, but not in distal tubule or collecting duct cells. Since adenosine has been demonstrated to elicit renal vasoconstriction and is produced by the ischemic kidney, it is suggested that adenosine may be involved in the mediation of postocclusion renal ischemia.

Isolation and characterization of N6-succinyladenosine from human urine

From the urines of colon carcinoma patients and normal subjects we have isolated a nucleoside in which an amino group of aspartic acid is attached to the six position of purine ribonucleoside. The structure, N6-succinyladenosine, N-(9-B-D-ribofuranosylpurin-6-yl)aspartic acid was assigned on the basis of spectral data, chemical degradation, and by synthesis. The ultraviolet and mass spectra, chromatographic and electrophoretic mobilities, and the chemical properties of the naturally occurring nucleoside were identical to those of the synthetic N6-succinyladenosine. In contrast to the methylated and hypermodified nucleosides which are products of RNA catabolism, this urinary nucleoside appears to be derived from adenylosuccinic acid, a key intermediate required in the biosynthesis of ubiquitous, natural purine nucleotide adenosine-5'-monophosphate (AMP).

Modified nucleosides in urine: selective removal and analysis

Because excretion of certain nucleosides increases in all types of cancer, detection and treatment of the disease would be enhanced by rapid, simple quantitation of such nucleotides. To facilitate these analyses in urine, we have prepared a specific adsorbent for nucleosides. The affinity adsorbent gel contains an immobilized phenylboronic acid group that specifically binds cis-diols, as in ribonucleosides, which can then be quantititatively recovered by elution with acetic acid. The advantage of this boronate gel over other preparations lies in its high capacity in the swollen state (0.26 mmol/ml), so that only small volumes (less than 1 ml) of gel are required for assays. Nucelosides containing a free diol group on the ribosyl group are retained at pH 8.8 in 0.25 mol/liter salt solution with a retention volume of 15 or larger, as compared with values of 1 to 2 for the free bases. Negatively charged species (not including the boronate complex) are eluted earlier than neutral or cationic species. Added nucleosides (neutral, cationic, or anionic) are quantitatively recovered. Because pseudouridine is eluted in a unique position, this property has been used to measure it in urine. The procedures used are chemically mild. For example, we have confirmed the observation of Fink and Adams [Arch. Biochem. Biophys. 126, 27 (1968)] that urine contains N1-methyladenosine and not N6-methyladenosine, the alkaline rearranged product.