Dahnke H G, Mosebach K O
Hoppe Seylers Z Physiol Chem. 1975 Oct;356(10):1565-74.
3H-labelled metabolites were determined in the perchloric acid-soluble fraction of blood plasma and liver of adult male Wistar rats, following the application of [5 - 3H]uridine. Ten minutes after the injection of uridine, only 20% of the total 3H activity of the plasma could be attributed to [3H]uridine. The remaining radioactivity was found chiefly in [3H]uracil (40%) and 3H2O (20%). In the liver, at 10 min, [3H]-uridine and [3H]uracil together accounted for less than 0.5% of the total radioactivity; about 70% of the radioactivity was due to [3H]beta-alanine, and 15% to 3H2O. 45 min after the injection, 70% of the radioactivity in the plasma was due to 3H2O, whereas uridine and uracil represented about 4% and 6%, respectively. At this time, about 55% of the radioactivity in the liver was due to [3H]beta-alanine, about 40% to 3H2O, and about 5% to unidentified metabolites; [3H]uridine and [3H]uracil were not observed. A comparison of the rate of catabolism of [5-3H]-uridine, [5-3H]cytidine and [6-3H]thymidine showed that cytidine is degraded in the organism 25 times more slowly than uridine or thymidine. The biological half lives for the total degradation of the [3H]nucleosides to 3H2O, based on the values in the plasma, were: uridine 1.1 h; thymidine 1.3 h; cytidine 25 h. Furthermore, the turnover time of exogenous uridine in the plasma was found to be 9 min, which gives a half life of 6 min for the metabolism of exogenous uridine to uracil.
给成年雄性Wistar大鼠注射[5 - ³H]尿苷后，测定其血浆和肝脏高氯酸可溶部分中的³H标记代谢物。注射尿苷10分钟后，血浆中³H总活性的仅20%可归因于[³H]尿苷。其余放射性主要存在于[³H]尿嘧啶（40%）和³H₂O（20%）中。在肝脏中，10分钟时，[³H]尿苷和[³H]尿嘧啶合起来占总放射性的不到0.5%；约70%的放射性归因于[³H]β-丙氨酸，15%归因于³H₂O。注射45分钟后，血浆中70%的放射性归因于³H₂O，而尿苷和尿嘧啶分别约占4%和6%。此时，肝脏中约55%的放射性归因于[³H]β-丙氨酸，约40%归因于³H₂O，约5%归因于未鉴定的代谢物；未观察到[³H]尿苷和[³H]尿嘧啶。[5 - ³H]尿苷、[5 - ³H]胞苷和[6 - ³H]胸苷分解代谢速率的比较表明，胞苷在生物体内的降解速度比尿苷或胸苷慢25倍。根据血浆中的值，[³H]核苷完全降解为³H₂O的生物半衰期为：尿苷1.1小时；胸苷1.3小时；胞苷25小时。此外，发现血浆中外源尿苷的周转时间为9分钟，这使得外源尿苷代谢为尿嘧啶的半衰期为6分钟。
