Gregory J F, Bhandari S D, Bailey L B, Toth J P, Baumgartner T G, Cerda J J
Food Science and Human Nutrition Department, University of Florida, Gainesville 32611-0163.
Am J Clin Nutr. 1992 Jun;55(6):1147-53. doi: 10.1093/ajcn/55.6.1147.
The bioavailability of orally administered monoglutamyl folic acid and various (6S)-tetrahydrofolates was examined in humans with stable-isotope methods. Folic acid (PteGlu), tetrahydrofolate (H4folate), 5-formyl-H4folate, 10-formyl-H4folate, and 5-methyl-H4folate were prepared for oral administration in 3',5'-2H2 labeled (d2) form, and [glu-2H4]folic acid (d4-PteGlu) was prepared for intravenous injection. In each of five trials, fasting adult males (n = 7) on a folate saturation regimen (2 mg/d) were given a single oral dose of one of the d2-folates in apple juice, as well as an intravenous injection of d4-PteGlu as a control. Urine was collected for 48 h and the isotope labeling of urinary folates determined by mass spectrometry. Isotope excretion ratios of urinary folates were used as criteria of bioavailability (pooled SE = 0.10): PteGlu (1.53, least squares mean), 10-formyl-H4folate (1.02), 5-methyl-H4folate (0.99), 5-formyl-H4folate (0.1.13), and H4folate (0.71). These results indicate that differences exist in the bioavailability of monoglutamyl folates under these experimental conditions. This variation, whether due to differences in absorption or postabsorptive events, must be considered in quantitative studies of folate utilization with this type of protocol.
采用稳定同位素方法在人体中研究了口服单谷氨酰叶酸和各种（6S）-四氢叶酸的生物利用度。将叶酸（蝶酰谷氨酸，PteGlu）、四氢叶酸（H4folate）、5-甲酰基-H4folate、10-甲酰基-H4folate和5-甲基-H4folate制备成3',5'-2H2标记（d2）形式用于口服给药，将[谷氨酰胺-2H4]叶酸（d4-PteGlu）制备成用于静脉注射。在五项试验中的每一项中，对处于叶酸饱和方案（2mg/d）的空腹成年男性（n = 7）给予单剂量的一种d2-叶酸口服，以苹果汁送服，同时静脉注射d4-PteGlu作为对照。收集尿液48小时，并通过质谱法测定尿叶酸的同位素标记。尿叶酸的同位素排泄率用作生物利用度的标准（合并标准误 = 0.10）：PteGlu（1.53，最小二乘均值）、10-甲酰基-H4folate（1.02）、5-甲基-H4folate（0.99）、5-甲酰基-H4folate（0.1.13）和H4folate（0.71）。这些结果表明，在这些实验条件下单谷氨酰叶酸的生物利用度存在差异。在采用此类方案进行的叶酸利用定量研究中，必须考虑这种差异，无论其是由于吸收差异还是吸收后事件所致。
