IRON ABSORPTION BY INFANTS

在正常和缺铁的成年人中，80%至90%的吸收的铁被迅速吸收。 掺入红细胞，以及红细胞掺入 因此，施用的铁同位素可用作铁的估计值。 吸收，而不是更困难和昂贵的代谢平衡 法 我们目前对成年人铁吸收的大部分知识 通过放射性同位素的红细胞掺入研究获得 铁。 反对使用放射性同位素进行类似的研究， 婴儿现在可以通过使用铁的稳定同位素来规避， 对获得的数据进行满意的解释需要以下信息： 婴儿红细胞铁结合的程度 预测铁的吸收。 利用铁的稳定同位素~（58）Fe，我们提出了同时测定 测定红细胞58 Fe掺入量， 假设：（1）与普遍持有的假设相反，正常术语 婴儿在生命的前4个月和以后一样有效地吸收铁 在婴儿期。 (2)基本上少于80%的吸收的铁被迅速吸收， (i.e.,在14天内）被婴儿掺入红细胞，至少 4个月以下的婴儿。 (3)饮食中的铁含量是 确定提示程度的主要因素（即，14天内） 口服铁同位素进入红细胞。 为实现具体目标1，将在以下地点开展58项铁平衡研究： 一个完全纵向的设计，每12名婴儿研究，在每4 年龄（1、2、4和8个月）。 粪便收集将在家中进行，直到 粪便中58 Fe含量恢复到基线值。 完成 具体目标2，我们将确定提示（即，14天内） 研究的同一婴儿的红细胞掺入58 Fe标记， 具体目标1。 为了实现具体目标3，我们将确定 在2组12名婴儿中促进红细胞铁结合。 在给予58 Fe后，一组将喂食含铁配方奶粉 另一个将被喂食铁含量为1 mg/L的配方奶粉， 12毫克/升。 血液和粪便中的58 Fe测定将使用新的 Finnigan Sola ICP/MS仪器。

In normal and iron-deficient adults, 80 to 90% of absorbed iron is promptly incorporated into erythrocytes, and erythrocyte incorporation of an administered iron isotope can therefore be used as an estimate of iron absorption rather than the more difficult and expensive metabolic balance method. Much of our current knowledge about iron absorption by adults has been obtained through studies of erythrocyte incorporation of radioisotopes of iron. The objection to using radioisotopes for similar studies of infants can now be circumvented by use of stable isotopes of iron, but satisfactory interpretation of the data obtained requires information about the extent to which erythrocyte incorporation of iron by infants is predictive of iron absorption. Using the stable isotope of iron, 58Fe, we propose concurrent determination of 58Fe balance and erythrocyte incorporation of 58Fe to test the following hypotheses: (1) Contrary to a widely held supposition, normal term infants absorb iron as efficiently during the first 4 mo of life as later in infancy. (2) Substantially less than 80% of absorbed iron is promptly (i.e., within 14 days) incorporated into erythrocytes by infants, at least by infants less than 4 mo of age. (3) The level of iron in the diet is a major factor determining the extent of prompt (i.e., within 14 d) incorporation of an orally administered iron isotope into erythrocytes. To accomplish Specific Aim 1, 58 Fe balance studies will be carried out in a fully longitudinal design with each of 12 infants studied at each of 4 ages (1, 2, 4 and 8 mo). Fecal collections will be made in the home until the 58Fe content of feces returns to baseline values. To accomplish Specific Aim 2, we shall determine the prompt (i.e., within 14 d) erythrocyte incorporation of the 58Fe label in the same infants studied in Specific Aim 1. To accomplish Specific Aim 3, we shall determine the prompt erythrocyte incorporation of iron in 2 groups of 12 infants each. After administration of 58Fe, one group will be fed a formula with iron content of 1 mg/L and the other will be fed a formula with iron content of 12 mg/L. 58Fe determinations in blood and feces will be made with the new Finnigan Sola ICP/MS instrument.