Urinary excretion of nucleosides varies with age and protein metabolism

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Urinary nucleosides

The methods of analysis, origins, and clinical significance of urinary nucleosides are reviewed through 1997. Structures, chromatographic and mass spectral data and references to the clinical literature are presented for each of the 57 nucleosides currently identified in normal and pathogenic human urine samples. Data from the HPLC separation and GC/MS analysis of 37 individual HPLC fractions are presented and discussed. Methods, including sample preparation techniques, used for the analysis of urinary nucleosides including GC, HPLC, GC/MS, HPLC/MS and immunoassays are compared and the advantages and limitations of each method described. The conclusion is drawn that the urinary nucleosides do serve as biomarkers of cancer and other diseases, but analytical methods need further improvement if clinical decisions are to be made based on the levels of nucleosides in human urine.

Quantitation of urinary nucleosides by high-performance liquid chromatography

It is known that some modified, especially methylated, nucleosides originating from RNA degradation are excreted in abnormal levels in the urine of patients with malignant tumours and they have been proposed as tumour markers. Their measurement could provide a non-invasive diagnostic method, be helpful in the identification of different cancers and in the monitoring of therapeutic effects. In this study, we developed and optimized an analytical procedure to isolate and quantify normal and modified ribonucleosides. The extraction of urinary nucleosides was performed by affinity chromatography on a phenylboronic acid column prior to separation. The reversed-phase high-performance liquid chromatography method allowed a complete separation of sixteen urinary ribonucleosides. The recoveries for the different nucleosides ranged from 83 to 100%, except for xanthosine (66%) and pseudouridine (74%). In normal 24 h urine, the mean levels of thirteen nucleosides (in nmol of nucleoside/mumol of creatinine) were found to be as follows: dihydrouridine (6.37), pseudouridine (25.52), cytidine (0.07), uridine (0.21), 1-methyladenosine (2.19), inosine (0.30), guanosine (0.06), xanthosine (0.59), 3-methyluridine (0.11), 1-methylinosine (1.13). 1-methylguanosine (0.74), adenosine (0.21) and 5'-deoxy-5'-methylthioadenosine (0.12). The first results concerning two kinds of tumours, i.e. breast and floor of mouth tumours, showed some abnormal levels of ribonucleosides. Further experiments are now in progress to measure the modified nucleosides in urine of patients with different forms of cancer.