Calbindin-D9k stimulates the calcium pump in rat enterocyte basolateral membranes.
Calbindin-D9k stimulates the calcium pump in rat enterocyte basolateral membranes.
复制标题
Calbindin-D9k 刺激大鼠肠细胞基底外侧膜中的钙泵。
DOI：
10.1152/ajpgi.1989.256.1.g124
复制
发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Walters,JR
中科院分区：
文献类型：
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作者：
Walters,JR
Calbindin-D9k是一种依赖维生素D的钙结合蛋白，与哺乳动物肠道细胞对钙的跨细胞吸收密切相关。研究了生理浓度的Calbindin-D9k是否改变了大鼠十二指肠基底外侧膜囊泡上依赖于ATP的钙泵对钙的转运。在用EGTA缓冲游离钙的溶液中，只能表现出对钙摄取速率的少量刺激，这可能是由于游离钙浓度的变化而引起的。然而，当使用无EGTA的溶液时，发现30微米的Calbindin-D9k对摄取有三倍的刺激作用，并避免了游离Ca~(2+)活性或45Ca~(2+)比活性的变化。该体系对钙离子的亲和力降低，但可被钙结合蛋白-D9K或EGTA刺激。研究发现，在没有EGTA的情况下，结合微摩尔范围内的钙离子的其他钙结合蛋白可以增加钙离子的摄取。这些实验表明，Calbindin-D9k的作用之一是通过增加Ca~(2+)泵对Ca~(2+)的转运来刺激Ca~(2+)从肠细胞中排出。
Calbindin-D9k, a vitamin D-dependent Ca2+-binding protein, is closely associated with the transcellular absorption of calcium by mammalian enterocytes. Studies were performed to determine whether physiological concentrations of calbindin-D9k altered Ca2+ transport by the ATP-dependent Ca2+ pump in rat duodenal basolateral membrane vesicles. In solutions where free Ca2+ was buffered by EGTA, only a small stimulation of Ca2+ uptake rates could be demonstrated, and it was likely that this was secondary to changes in free Ca2+ concentration. However, a threefold stimulation of uptake by 30 microM calbindin-D9k was found when EGTA-free solutions were used, and changes in free Ca2+ activity or 45Ca2+ specific activity were avoided. The affinity for Ca2+ was reduced in this system but appeared to be stimulated by either calbindin-D9k or EGTA. Other Ca2+-binding proteins that bind Ca2+ in the micromolar range were found to increase Ca2+ uptake in the absence of EGTA. These experiments suggest that one of the actions of calbindin-D9k is to stimulate the rate of extrusion of Ca2+ from the enterocyte by increasing Ca2+ transport by the Ca2+ pump.