Tani M, Iwai K
J Nutr. 1984 Apr;114(4):778-85. doi: 10.1093/jn/114.4.778.
The excretions of folate compounds into both the urine and bile were investigated in rats after the administration of pteroylglutamic acid (PteGlu) with or without the folate-binding protein (FBP) prepared from bovine milk. When the sample solution, containing either free or bound [3H]PteGlu (i.e., bound to the FBP from milk), was delivered to rats intragastrically via oral intubation, the amounts of [3H]PteGlu excreted into the feces did not change. On the other hand, the urinary excretion of 3H-labeled folate compounds, especially [3H]5-methyltetrahydrofolic acid (5-CH3-H4PteGlu), after the administration of bound [3H]PteGlu was significantly lower (P less than 0.01) than that after the administration of free [3H]PteGlu. The urinary excretion of [3H]5-CH3-H4PteGlu was directly proportional to the initial amount of free [3H]PteGlu administered. The similar effect of FBP was also observed when the biliary excretion of 3H-labeled folate compounds was investigated in situ. Furthermore, the incorporation of [3H]PteGlu into folate-requiring intestinal microorganisms was considerably reduced when it was bound to FBP. These results suggest that milk FBP has some nutritional effects on the bioavailability of folate in vivo.
在给大鼠施用蝶酰谷氨酸（PteGlu）时，无论是否添加从牛奶中制备的叶酸结合蛋白（FBP），都对大鼠尿液和胆汁中叶酸化合物的排泄情况进行了研究。当含有游离或结合型[3H]PteGlu（即与牛奶中的FBP结合）的样品溶液通过口服插管经胃内给予大鼠时，排泄到粪便中的[3H]PteGlu量没有变化。另一方面，给予结合型[3H]PteGlu后，3H标记的叶酸化合物，尤其是[3H]5-甲基四氢叶酸（5-CH3-H4PteGlu）的尿排泄量显著低于（P<0.01）给予游离[3H]PteGlu后的尿排泄量。[3H]5-CH3-H4PteGlu的尿排泄量与给予的游离[3H]PteGlu的初始量成正比。在原位研究3H标记的叶酸化合物的胆汁排泄时，也观察到了FBP的类似作用。此外，当[3H]PteGlu与FBP结合时，其在需要叶酸的肠道微生物中的掺入量大大减少。这些结果表明，牛奶FBP对体内叶酸的生物利用度具有一些营养作用。
