Jejunal and ileal adaptation to alterations in dietary calcium: changes in calcium and magnesium absorption and pathogenetic role of parathyroid hormone and 1,25-dihydroxyvitamin D.
Jejunal and ileal adaptation to alterations in dietary calcium: changes in calcium and magnesium absorption and pathogenetic role of parathyroid hormone and 1,25-dihydroxyvitamin D.
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空肠和回肠对膳食钙变化的适应：钙和镁吸收的变化以及甲状旁腺激素和 1,25-二羟基维生素 D 的致病作用。
DOI：
10.1172/jci110194
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Pak,CY
中科院分区：
文献类型：
--
作者：
Norman,DA;Fordtran,JS;Brinkley,LJ;Zerwekh,JE;Nicar,MJ;Strowig,SM;Pak,CY
以前的平衡研究表明，低钙饮食会增加部分钙的吸收，而高钙饮食会减少部分钙的吸收。目前的研究是为了确定小肠的哪一部分对膳食钙的变化最敏感，以及膳食钙摄入量是否对另一种二价阳离子镁的肠道吸收有影响。分别在高钙饮食(1900 mg/d)和低钙饮食(20 mg/d)饮食4周或8周后，对正常受试者持续灌流30 cm长的空肠和回肠进行吸收测定。我们发现，与高钙饮食相比，受试者在低钙饮食时的钙吸收率更高；回肠的反应比空肠更快、更完整。使用镁也得到了类似的结果，但只有回肠的差异有统计学意义。钠和木糖的吸收不受膳食钙摄入量的影响。低钙组血清甲状旁腺激素和1，25-二羟基维生素D浓度高于高钙组。我们的结论是，回肠比空肠对饮食钙摄入量的变化更敏感，回肠适应可能在保护身体免受身体钙缺乏或过剩的影响方面发挥重要作用，否则当饮食钙异常低或高时就会发生这种情况。钙的摄入以类似的方式影响回肠镁的吸收；目前还不知道这是否起到保护作用。我们的数据与饮食钙摄入量的适应是通过血清甲状旁腺激素和1，25-二羟基维生素D浓度变化来调节的概念是一致的。
Previous balance studies have shown that fractional calcium absorption is increased by a low and reduced by a high calcium diet. The present studies were done to determine which segment of the small intestine is most sensitive to alterations in dietary calcium, and to see if dietary calcium intake has an effect on the intestinal absorption of another divalent cation, magnesium. Absorption was measured during constant perfusion of 30-cm segments of jejunum and ileum of normal subjects after 4 or 8 wk of a high (1,900 mg/d) or a low (20 mg/d) calcium diet. We found that calcium absorption rate was higher when subjects had been on a low than when they had been on a high calcium diet; the ileum responded more rapidly and more completely than the jejunum. Similar results were obtained with magnesium, but only the difference in the ileum was statistically significant. Sodium and xylose absorption were not influenced by dietary calcium intake. The serum concentrations of parathyroid hormone and 1,25-dihydroxyvitamin D were higher on the low than on the high calcium diet. We conclude that the ileum is more sensitive than the jejunum to changes in dietary calcium intake, and that ileal adaptation probably plays a major role in protecting the body against a deficiency or excess of body calcium that otherwise would occur when dietary calcium is abnormally low or high. Calcium intake influences ileal magnesium absorption in a similar fashion; it is not known whether or not this serves a protective function. Our data are compatible with the concept that adaptation to dietary calcium intake is mediated by changes in the serum concentrations of parathyroid hormone and 1,25-dihydroxyvitamin D.