[The effect of dietary purines and pyrimidines on human pyrimidine biosynthesis].

Young healthy volunteers received a purine-free, isoenergetic formula diet over a period of 28 to 32 days. After a short time under formula diet alone 400 mg allopurinol were administered daily. After a further 10 days each volunteer received daily, in addition, either 4 g RNA, 4 g RNA-hydrolysate, 1 g guanosine-5-monophosphate (GMP), 1 or 3 g adenosine-5-monophosphate (AMP), uridine-5-monophosphate (UMP), cytidine-5-monophosphate (CMP) or adenosine, guanosine, uridine, cytidine, guanine, hypoxanthine, xanthine, cytosine and uracil. Finally the allopurinol was omitted. The renal excretion of total orotic acid (orotic acid and orotidine), uric acid and creatinine was determined daily; serum uric acid concentrations and the enzyme activities of orotidine-5-phosphate-decarboxylase (ODCase) and hypoxanthine-guanine-phosphoribosyltransferase (HGPRTase) from erythrocytes were determined every other day. The results show that RNA, RNA-hydrolysate, purine- and pyrimidine-nucleotides and -nucleotides as well as hypoxanthine, and to a lesser extent adenine, diminish allopurinol-induced orotaciduria. This is compatible with an influence of dietary purines and pyrimidines on human pyrimidine biosynthesis.