Koshiishi I, Mamura Y, Liu J, Imanari T
Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Biochim Biophys Acta. 1998 Sep 16;1425(1):209-14. doi: 10.1016/s0304-4165(98)00073-7.
In our previous paper (Biochim. Biophys. Acta 1379 (1998) 257-263), we demonstrated that bicarbonate promotes a cleavage of lactone ring of dehydroascorbate (DHA) on the basis of in vitro experiments. In the present study, we examined the degradation of DHA in blood circulation in vivo by using a high-performance liquid chromatographic method for the determination of ascorbate (AsA), DHA and 2,3-diketogulonate (2,3-DKG), which required no pretreatment of biological fluids. When DHA was intravenously administered to rats, a rapid disappearance of DHA (t1/2 < 1 min) and a concomitant appearance of 2,3-DKG in blood circulation were observed. Approximately 90% of the administered DHA were excreted into urine as resulting 2,3-DKG (55%) and AsA (31%), respectively. Furthermore, we elucidated that rat plasma lacks an enzyme having an aldonolactonase-like activity. The result of the present study suggests that this DHA disappearance is a function of both a chemical degradation to 2,3-DKG and a reduction to AsA.
在我们之前的论文（《生物化学与生物物理学报》1379 (1998) 257 - 263）中，我们基于体外实验证明了碳酸氢盐能促进脱氢抗坏血酸（DHA）内酯环的裂解。在本研究中，我们使用一种无需对生物流体进行预处理的高效液相色谱法来测定抗坏血酸（AsA）、DHA和2,3 - 二酮古洛糖酸（2,3 - DKG），以此研究DHA在体内血液循环中的降解情况。当向大鼠静脉注射DHA时，观察到DHA在血液循环中迅速消失（t1/2 < 1分钟），同时出现2,3 - DKG。所注射的DHA中约90%分别以生成的2,3 - DKG（55%）和AsA（31%）的形式排泄到尿液中。此外，我们阐明了大鼠血浆缺乏具有醛糖内酯酶样活性的酶。本研究结果表明，这种DHA的消失是化学降解为2,3 - DKG和还原为AsA这两种作用的结果。
