[Studies on nucleic acid metabolism. Molecular biology and clinical significance].

All known nucleic acids contain varying amounts of modified nucleosides. In contrast to the standard nucleosides, the modified nucleosides and their nucleobases as minor nucleic acids components cannot be recycled. Only part of them can be catabolized. Therefore, many modified catabolites of nucleic acids are enriched in urine. They can be measured at the picomole level by cation exchange HPLC. Plotted against age, the excretion curves of the modified nucleobases are in accordance with the shape of the known growth velocity curve. Aberrant nucleobases excretion patterns are found in very young children, probably resulting from a specific nucleic acids equipment as well as from different relative growth velocities of different organs. In the urine of patients with neoplasms, often extremely disturbed nucleobases excretion patterns are found which can be normalized by successful cytostatic therapy. From the published and our own results it is concluded that modifications of nucleic acids should play an important regulatory role. Therefore, the analysis of modified nucleobases excretion patterns will open new diagnostic approaches.