IRON ABSORPTION BY INFANTS

在正常和缺铁的成年人中，80%到90%的吸收的铁被迅速 掺入红细胞，红细胞掺入一种 因此，服用的铁同位素可用作铁的估计值。 而不是更难和更昂贵的代谢平衡 方法。我们目前关于成年人铁吸收的大部分知识都有 是通过研究红细胞掺入放射性同位素而获得的 铁制的。反对将放射性同位素用于类似的研究 婴儿现在可以通过使用稳定的铁同位素来避开，但 对所获得的数据进行令人满意的解释需要以下方面的信息 婴儿红细胞对铁的掺入程度是 可以预测铁的吸收。 利用铁的稳定同位素--~(58)Fe，我们建议同时测定 ~(58)Fe平衡和红细胞~(58)Fe掺入试验 假设：(1)与普遍认为的假设相反，正常条件 婴儿在生命的前4个月吸收铁的效率与以后一样高 在婴儿期。(2)被迅速吸收的铁大大少于80% (即，在14天内)至少由婴儿并入红细胞 不到4个月大的婴儿。(3)饮食中的铁含量是 决定及时程度的主要因素(即在14天内) 将口服的铁同位素掺入红细胞中。 为达到特定目标，将在#年进行58项铁平衡研究。 一项完全纵向的设计，每个婴儿12个，每个婴儿4个 年龄(1、2、4和8mo)。粪便收集将在家中进行，直到 粪便中58Fe含量恢复到基准值。要完成 具体目标2，我们将确定提示(即在14天内) 年研究的同一婴儿的红细胞对58Fe标记的掺入 具体目标1.为实现具体目标3，我们将确定 促进两组婴儿红细胞铁的掺入，每组12例。 在服用58Fe后，其中一组将喂食含铁配方奶粉 铁含量为1毫克/L的配方奶粉和另一种铁含量为 12 mg/L。58血和粪便中铁的测定将用新的 芬兰索拉电感耦合等离子体质谱仪。

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.