A Rapid Assay for Urinary Pteridine Levels for Monitoring Cancer

Abstract

Pteridines are normally excreted in urine by healthy normal subjects but are significantly elevated during certain disease states associated with an activated cellular immune system. A simple method for estimation of total urinary pteridines has been developed, in which a 50-fold dilution of the urine sample was made to relieve the observed quenching of the fluorescence emitted by pteridines in the undiluted sample. The reduced pteridine derivatives were oxidized with iodine to their fluorescence-emitting fully oxidized forms, followed by direct measurement of fluorescence at 450nm with excitaiton at 360nm. The estimated total urinary pteridines were expressed as μg per mg creatinine. Employing this technique, we observed highly significant differences in excretion of total urinary pteridines between cancer patients and controls. Results were found to be as informative as those obtained by the standard selective estimation of urinary neopterin after reverse-phase high-performance liquid chromatographic separation. This rapid test requires only a small quantity of sample and has the potential to be developed into a routine clinical method for preliminary diagnosis and monitoring of cancer patients and for screening potential blood donors.