Tactacan G B, Rodriguez-Lecompte J C, Karmin O, House J D
Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, Canada.
Poult Sci. 2011 Jan;90(1):83-90. doi: 10.3382/ps.2010-01029.
Absorption at the level of the intestine is likely a primary regulatory mechanism for the deposition of dietary supplemented folic acid into the chicken egg. Therefore, factors affecting the intestinal transport of folic acid in the laying hen may influence the level of egg folate concentrations. To this end, a series of experiments using intestinal everted sacs were conducted to characterize intestinal folic acid absorption processes in laying hens. Effects of naturally occurring folate derivatives (5-methyl and 10-formyltetrahydrofolate) as well as heme on folic acid absorption were also investigated. Folic acid absorption was measured based on the rate of uptake of (3)H-labeled folic acid in the everted sac from various segments of the small and large intestines. Folic acid concentration, incubation length, and pH condition were optimized before the performance of uptake experiments. The distribution profile of folic acid transport along the intestine was highest in the upper half of the small intestine. Maximum uptake rate (nmol·100 g tissue(-1)·min(-1)) was observed in the duodenum (20.6 ± 1.9) and jejunum (22.3 ± 2.0) and decreased significantly in the ileum (15.3 ± 1.1) and cecum (9.3 ± 0.9). Transport increased proportionately (P < 0.05) between 0.0001 and 0.1 µM folic acid. Above 0.1 µM, the slope of the regression line was not significantly different from zero (P < 0.137). Folic acid uptake in the jejunum showed a maximum rate of transport at pH 6.0, but was lowest at pH 7.5. The presence of 5-methyl and 10-formyltetrahydrofolate as well as heme impeded folic acid uptake, reducing intestinal folic acid absorption when added at concentrations ranging from 0 to 100 µM. Overall, these data indicated the presence of a folic acid transport system in the entire intestine of the laying hen. Uptake of folic acid in the cecum raises the likelihood of absorption of bacterial-derived folate.
肠道水平的吸收可能是膳食补充叶酸沉积到鸡蛋中的主要调节机制。因此，影响产蛋母鸡肠道叶酸转运的因素可能会影响蛋中叶酸浓度水平。为此，进行了一系列使用肠外翻囊的实验，以表征产蛋母鸡肠道叶酸吸收过程。还研究了天然存在的叶酸衍生物（5-甲基和10-甲酰基四氢叶酸）以及血红素对叶酸吸收的影响。基于小肠和大肠各段外翻囊中（3）H标记叶酸的摄取速率来测量叶酸吸收。在进行摄取实验之前，对叶酸浓度、孵育时间和pH条件进行了优化。叶酸沿肠道的转运分布在上半段小肠中最高。在十二指肠（20.6±1.9）和空肠（22.3±2.0）中观察到最大摄取速率（nmol·100 g组织（-1）·min（-1）），在回肠（15.3±1.1）和盲肠（9.3±0.9）中显著降低。在0.0001至0.1 µM叶酸之间，转运成比例增加（P<0.05）。高于0.1 µM，回归线的斜率与零无显著差异（P<0.137）。空肠中的叶酸摄取在pH 6.0时显示出最大转运速率，但在pH 7.5时最低。5-甲基和10-甲酰基四氢叶酸以及血红素的存在阻碍了叶酸摄取，当以0至100 µM的浓度添加时会降低肠道叶酸吸收。总体而言，这些数据表明产蛋母鸡整个肠道中存在叶酸转运系统。盲肠中叶酸的摄取增加了细菌衍生叶酸吸收的可能性。
