QUANTITATION OF URINARY NUCLEOSIDES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

It is known that some modified, especially methylated, nucleosides ori ginating from RNA degradation are excreted in abnormal levels in the u rine of patients with malignant tumours and they have been proposed as tumour markers. Their measurement could provide a non-invasive diagno stic 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 wa s performed by affinity chromatography on a phenylboronic acid column prior to separation. The reversed-phase high-performance liquid chroma tography method allowed a complete separation of sixteen urinary ribon ucleosides. The recoveries for the different nucleosides ranged from 8 3 to 100%, except for xanthosine (66%) and pseudouridine (74%). In nor mal 24 h urine, the mean levels of thirteen nucleosides (in nmol of nu cleoside/mu mol of creatinine) were found to be as follows: dihydrouri dine (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-methylguanos ine (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 nucl eosides in urine of patients with different forms of cancer.