Kaune R
Department of Physiology, School of Veterinary Medicine Hannover, Germany.
Dtsch Tierarztl Wochenschr. 1996 Jun;103(6):215-8.
Calcium absorption from the intestine may be active via the transcellular route or passive via the paracellular route, but the active component is necessary for the maintenance of calcium homeostasis. The active transport depends on vitamin D and is more restricted to the proximal part of the small intestine. Calcitriol, the active metabolite of vitamin D, induces the synthesis of calbindin, a Ca(2+)-binding protein which seems to be involved in transcellular Ca(2+)-transport, increases the number of Ca(2+)-transport components in the apical membrane, but is without direct influence on Ca(2+)-pumps of the basolateral membrane. A phytate-phosphorus containing diet not only reduces the availability of phosphorus but also of calcium. However, with sufficient supply of vitamin D, this may be compensated by the hormonal regulation of calcium homeostasis. Addition of lactose to the diet increases the apparent digestibility of calcium in the postileal segment of the gastrointestinal tract by an so far unknown mechanism.
钙可通过跨细胞途径经主动方式从肠道吸收，或通过细胞旁途径经被动方式吸收，但主动成分对于维持钙稳态是必需的。主动转运依赖维生素D，且更局限于小肠近端。维生素D的活性代谢产物骨化三醇可诱导钙结合蛋白的合成，钙结合蛋白是一种似乎参与跨细胞钙转运的Ca(2+)结合蛋白，可增加顶端膜中Ca(2+)转运成分的数量，但对基底外侧膜的Ca(2+)泵无直接影响。含植酸盐磷的饮食不仅会降低磷的利用率，还会降低钙的利用率。然而，在维生素D供应充足的情况下，这可能会通过钙稳态的激素调节得到补偿。在饮食中添加乳糖可通过一种迄今未知的机制提高胃肠道回肠段钙的表观消化率。
