Role of vitamin D-dependent and vitamin D-independent mechanisms in absorption of food calcium.
Role of vitamin D-dependent and vitamin D-independent mechanisms in absorption of food calcium.
复制标题
维生素 D 依赖性和维生素 D 独立机制在食物钙吸收中的作用。
DOI：
10.1172/jci113283
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Fordtran,JS
中科院分区：
文献类型：
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作者：
Sheikh,MS;Ramirez,A;Emmett,M;SantaAna,C;Schiller,LR;Fordtran,JS
我们测量了血清中1，25-二羟基维生素D(以下简称1，25-D)浓度差异很大的人群的净钙吸收和消化腺分泌物中的钙含量。血液透析的终末期肾病患者作为人类1，25-D缺乏的模型；当他们因短期外源性1，25-D治疗而导致血清1，25-D浓度异常高时，也进行了研究。以正常受试者为对照。消化腺分泌到十二指肠的钙量与正常或甚至低钙膳食的钙含量相比微不足道；因此，净钙吸收和真实净钙吸收的值只有很小的差别。真净钙吸收与血清1，25-D浓度呈线性相关。通过将短距离外推到血清1，25-D的零值，估计了非D依赖的真实净钙吸收。通过从真实的净钙吸收中减去独立于D的值，得到依赖于D的吸收的值。对于给定的膳食钙摄入量水平，D依赖的钙吸收被发现与血清1，25-D浓度成正比。在血清1，25-D的任何给定值下，低钙膳食(120毫克)通过D依赖机制的吸收与膳食钙摄入量增加到300毫克时大致相同。我们将此解释为低钙膳食饱和或接近饱和的依赖D的机制。不依赖D的吸收/分泌机制导致低摄入量(每餐120毫克)时的分泌(粪便中的体钙损失)和正常摄入量时的吸收。当低钙餐或正常钙餐补充额外的钙时，所有钙吸收的增加都是由D-非依赖性机制介导的。
We measured net calcium absorption and the calcium content of the digestive glands secretions in people with widely different serum concentrations of 1,25 dihydroxy vitamin D (hereafter referred to a 1,25-D). Patients with end stage renal disease on hemodialysis served as a model of human 1,25-D deficiency; they were also studied when they had abnormally high serum 1,25-D concentrations as a result of short periods of treatment with exogenous 1,25-D. Normal subjects were studied for comparison. The amount of calcium secreted into the duodenum by the digestive glands was found to be trivial compared to the calcium content of normal or even low calcium meals; therefore, values for net and true net calcium absorption differed only slightly. There was a linear correlation between true net calcium absorption and serum 1,25-D concentration. By extrapolating the short distance to a zero value for serum 1,25-D, D-independent true net calcium absorption was estimated. By subtracting D independent from true net calcium absorption, values for D-dependent absorption were obtained. For a given level of meal calcium intake, D-dependent calcium absorption was found to be directly proportional to serum 1,25-D concentration. At any given value for serum 1,25-D, absorption via the D-dependent mechanism was approximately the same with a low (120 mg) calcium meal as it was when meal calcium intake was increased to 300 mg. We interpret this to mean that the D-dependent mechanism is saturated or nearly saturated by low calcium meals. The D-independent absorption/secretion mechanism resulted in secretion (a loss of body calcium in the feces) when intake was low (120 mg per meal) and absorption when intake was normal. All of the increment in calcium absorption that occurs when low or normal calcium meals are supplemented with extra calcium is mediated by the D-independent mechanism.