Studies on the purine-pyrimidine metabolism (2)--Effects of sample preparation and diet on the concentrations of oxypurines in blood and urine.

The levels of pseudouridine (psi rd), uridine (Urd), hypoxanthine (Hyp), xanthine (Xan) and uric acid (UA) in both blood and urine samples were assayed by a reversed-phase high performance liquid chromatographic (HPLC) method. The evaluation of the sampling procedures showed that the levels of plasma oxypurines were overestimated by more than 15% for Hyp and 35% for Xan when heparinized plasma separation was delayed for 5 minutes after sampling. The fact that oxypurines levels of serum were significantly higher than those of plasma was also documented. Hence, for the accurate measurement of plasma oxypurines, plasma should be immediately separated from the blood with anticoagulants after it is collected. Physiological variation under a suitable sample preparation was also studied in 6 healthy male volunteers after their usual and a low purine diet for 4 days. The mean plasma levels for 6 male volunteers on a usual diet were 2.52 +/- 0.19 mumol/l for psi rd, 290.1 +/- 88.8 for UA, 49.4 +/- 1.24 for Urd, 0.82 +/- 0.30 for Hyp and 0.49 +/- 0.12 for Xan. On a low purine diet, the declines in the plasma oxypurine concentrations and the renal excretions of UA as well as oxypurine were demonstrated. When a dietary purine intake was restricted, the reference range of the Hyp level in plasma wa 0.48 +/- 0.26, and Xan was 0.36 +/- 0.17 mumol/l. Dietary influences on purine-pyrimidine metabolites should also be considered for the accurate measurement of their concentrations in blood and urine.