Kipp D E, Rivers J M
J Nutr. 1984 Aug;114(8):1386-95. doi: 10.1093/jn/114.8.1386.
The half-life of ascorbic acid (AA) in guinea pigs was investigated by the isotope dilution and excretion methods. The dilution method measures [1-14C]AA disappearance from the plasma, whereas the excretion method measures the elimination of [1-14C]AA and the metabolites from the body. Two groups of animals underwent both isotope studies in reverse order. Animals were conditioned to the experimental procedures and fed 2.5 mg AA/100 g body weight orally to maintain a daily intake of the vitamin independent of food consumption. The two isotope procedures imposed similar stress on the animals, as determined by plasma cortisol levels and body weight changes. The AA half-life calculations of the rapidly exchangeable pool by the isotope dilution method yielded values of 1.23 and 0.34 hours for the two groups, respectively. The half-life of the slowly exchangeable pool for the two groups was 60.2 and 65.8 hours, respectively. The half-life of AA in the rapidly exchangeable pool, as measured by the excretion studies, was 4.57-8.75 hours. For the slowly exchangeable pool, it was 146-149 hours. The longer half-life of both pools obtained with the excretion method indicates that the isotope is disappearing from the plasma more rapidly than it is being excreted. This suggests that a portion of the [1-14C]AA leaving the plasma is removed to a body pool that is not sampled by the isotope excretion method.
通过同位素稀释法和排泄法研究了豚鼠体内抗坏血酸（AA）的半衰期。稀释法测量血浆中[1-14C]AA的消失情况，而排泄法测量[1-14C]AA及其代谢产物从体内的消除情况。两组动物以相反顺序进行了这两种同位素研究。动物适应了实验程序，并口服2.5mg AA/100g体重，以维持与食物消耗无关的维生素每日摄入量。通过血浆皮质醇水平和体重变化确定，这两种同位素程序对动物施加的应激相似。通过同位素稀释法计算快速可交换池的AA半衰期，两组的值分别为1.23小时和0.34小时。两组缓慢可交换池的半衰期分别为60.2小时和65.8小时。通过排泄研究测量，快速可交换池中AA的半衰期为4.57 - 8.75小时。对于缓慢可交换池，其半衰期为146 - 149小时。排泄法获得的两个池的半衰期较长，这表明同位素从血浆中消失的速度比其排泄速度更快。这表明离开血浆的一部分[1-14C]AA被转移到了同位素排泄法未采样的体内池。
