ORIGIN OF INTACT LACTOFERRIN AND ITS DNA-BINDING FRAGMENTS FOUND IN THE URINE OF HUMAN MILK-FED PRETERM INFANTS - EVALUATION BY STABLE ISOTOPIC ENRICHMENT
ORIGIN OF INTACT LACTOFERRIN AND ITS DNA-BINDING FRAGMENTS FOUND IN THE URINE OF HUMAN MILK-FED PRETERM INFANTS - EVALUATION BY STABLE ISOTOPIC ENRICHMENT
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DOI：
10.1203/00006450-199103000-00005
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发表时间：
1991-03-01
影响因子：
3.6
通讯作者：
GARZA, C
中科院分区：
文献类型：
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作者：
HUTCHENS, TW;HENRY, JF;GARZA, C
利用富含[C-13]亮氨酸和[N-15(2)赖氨酸或[H-2(4)赖氨酸的人乳，研究了母乳喂养早产儿尿液中发现的完整（78-kD）乳铁蛋白的来源。被选中参加这项研究的婴儿的母亲静脉注射[C-13]亮氨酸和[N-2(15)]赖氨酸或[H-4(2)]赖氨酸来标记牛奶中的蛋白质。从每位母亲处收集标记的乳汁，将其混合，加入冻干人乳馏分，并通过连续灌胃喂养其早产儿48小时。收集每位婴儿的尿液96小时。通过固定单链dna -琼脂糖柱亲和层析从尿液中纯化完整的乳铁蛋白（78 kD）和dna结合乳铁蛋白片段（51和39 kD）。完整乳铁蛋白和dna结合片段经高效反相（苯基）色谱分离后，分别测定其浓度和同位素富集程度。质谱分析表明，纯化后的尿乳铁蛋白同位素丰度为标记的人乳乳铁蛋白的87 ~ 100%。分离的dna结合乳铁蛋白片段得到了类似的结果。纯化乳铁蛋白和尿乳铁蛋白中同位素标记的亮氨酸与赖氨酸的比例在每对母婴中相似。同位素标记的赖氨酸作为游离氨基酸添加到牛奶中，未掺入纯化的尿乳铁蛋白中。这些结果表明，母体来源的未降解（78-kD）乳铁蛋白被肠道吸收，并在早产儿的尿液中完整地排出；几乎所有的尿乳铁蛋白都来自母系。讨论了吸收完整的母系乳铁蛋白可能的免疫调节功能。
The origin of intact (78-kD) lactoferrin found in the urine of human milk-fed preterm infants was investigated using human milk containing proteins enriched with [C-13]leucine and [N-15(2)lysine or [H-2(4)lysine. Mothers of infants selected for the study were infused i.v. with [C-13] leucine and [N-2(15)]lysine or [H-4(2)]lysine to label milk proteins. The labeled milk was collected from each mother, pooled, fortified with a lyophilized human milk fraction, and fed to her preterm infant by continuous orogastric infusion for a period of 48 h. Urine was collected from each infant for 96 h. Intact lactoferrin (78 kD) and DNA-binding lactoferrin fragments (51 and 39 kD) were purified from the urine by affinity chromatography on columns of immobilized single-stranded DNA-agarose. The concentration and isotopic enrichment of the intact lactoferrin and DNA-binding fragments were determined separately after their isolation by high-performance reverse-phase (phenyl) chromatography. Mass spectral analyses indicated that the isotopic enrichment of the purified urinary lactoferrin was 87 to 100% of that in the labeled human milk lactoferrin. Similar results were obtained for the isolated DNA-binding lactoferrin fragments. The ratios of isotopically labeled leucine to lysine in the purified milk lactoferrins and urinary lactoferrins were similar for each mother/infant pair. Isotopically labeled lysine, added to the milk as free amino acid, was not incorporated into the purified urinary lactoferrin. These results demonstrate that undegraded (78-kD) lactoferrin of maternal origin is absorbed by the gut and excreted intact in the urine of preterm infants; nearly all of the urinary lactoferrin was of maternal origin. The possible immunoregulatory functions of the absorbed intact, maternal lactoferrin are discussed.