Lee W, Davis K A, Rettmer R L, Labbe R F
Department of Laboratory Medicine, University of Washington, Seattle 98195.
Am J Clin Nutr. 1988 Aug;48(2):286-90. doi: 10.1093/ajcn/48.2.286.
Ascorbic acid (AA) plus dehydroascorbic acid (DHAA) was stable in whole blood in unopened vacutainer tubes. Oxidation of DHAA in plasma was irreversible and rapid at 25 degrees C but not at 4 degrees C. The half-life of AA + DHAA in total parenteral nutrition solutions was greater than 24 h. Conditions are described for dithiothreitol reduction of DHAA followed by assay of total AA, with DHAA being determined by difference. DHAA accounted for less than 5% of the total plasma AA + DHAA in both healthy and diabetic subjects. Infection and postpartum-induced stresses resulted in no significant change in the AA content of polymorphonuclear leukocytes (PMN) per unit of blood but AA content per cell was decreased. When glucose concentration was increased, the Km for AA uptake by PMNs doubled. These chemical and physiological factors combined with the rapid movement of the vitamin between plasma and cells suggest that a reliable indicator of AA status remains to be identified.
抗坏血酸（AA）加脱氢抗坏血酸（DHAA）在未开封的真空采血管中的全血中是稳定的。血浆中DHAA的氧化在25℃时是不可逆且快速的，但在4℃时并非如此。全胃肠外营养溶液中AA + DHAA的半衰期大于24小时。描述了用二硫苏糖醇还原DHAA然后测定总AA的条件，其中DHAA通过差值法测定。在健康和糖尿病受试者中，DHAA占血浆总AA + DHAA的比例均小于5％。感染和产后引起的应激导致每单位血液中多形核白细胞（PMN）的AA含量无显著变化，但每个细胞的AA含量降低。当葡萄糖浓度增加时，PMN摄取AA的Km值加倍。这些化学和生理因素，再加上维生素在血浆和细胞之间的快速移动，表明仍有待确定一个可靠的AA状态指标。
