Seldin D W
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Tex. 75235, USA.
Nephron. 1999;81 Suppl 1:2-7. doi: 10.1159/000046292.
Ca absorption is mediated by both active and passive processes. Absorption in both proximal tubule and thick ascending limb is mainly coupled indirectly to Na absorption and is a passive process through the paracellular pathway. In the distal convoluted tubule, Ca absorption is regulated independently of Na absorption; this is the principal site of action of parathyroid hormone, calcitonin, and 1,25-(OH)2D3. Models for transport in proximal tubule, thick ascending limb, and distal convoluted tubule afford attractive explanations for the influence on Ca transport of effective arterial blood volume, parathyroid hormone, acid-base balance, genetic disturbances such as Bartter's and Gitelman's syndromes, and diuretic action.
钙的吸收由主动和被动过程介导。近端小管和髓袢升支粗段的吸收主要间接与钠的吸收耦联，是通过细胞旁途径的被动过程。在远曲小管，钙的吸收独立于钠的吸收进行调节；这是甲状旁腺激素、降钙素和1,25-(OH)₂D₃的主要作用部位。近端小管、髓袢升支粗段和远曲小管的转运模型，为有效动脉血容量、甲状旁腺激素、酸碱平衡、诸如巴特综合征和吉特曼综合征等遗传性疾病以及利尿剂作用对钙转运的影响，提供了有吸引力的解释。
