Nellans H N, Popovitch J E
J Biol Chem. 1981 Oct 10;256(19):9932-6.
Uptake of calcium by a membrane fraction enriched in basolateral plasma membrane vesicles from rat small intestine has been investigated using a rapid filtration technique. Calcium accumulation is stimulated by ATP and released by the calcium ionophore A23187. Kinetic studies indicate a calcium concentration of 28 nM for half-maximal stimulation of ATP-driven uptake. Transport is minimally inhibited by oligomycin and ouabain but is reduced 40% by lanthanum and abolished by 50 microM vanadate. The ATP-dependent calcium uptake is stimulated by the calcium regulatory protein, calmodulin, in a dose-dependent fashion. Calmodulin increases both the maximal transport rate and the calcium affinity of the transport mechanism. These results are consistent with the existence of an ATP-dependent, calmodulin-regulated calcium transport mechanism in the basolateral plasma membrane of intestinal epithelial cells, and suggests that calmodulin may modulate transepithelial calcium absorption in addition to controlling cytosolic calcium levels.
采用快速过滤技术，对富含大鼠小肠基底外侧质膜囊泡的膜部分对钙的摄取进行了研究。ATP刺激钙的积累，钙离子载体A23187可释放钙。动力学研究表明，ATP驱动摄取的半最大刺激所需的钙浓度为28 nM。寡霉素和哇巴因对转运的抑制作用最小，但镧可使转运减少40%，50 microM钒酸盐可使转运完全消除。钙调节蛋白钙调蛋白以剂量依赖的方式刺激ATP依赖的钙摄取。钙调蛋白增加了最大转运速率和转运机制对钙的亲和力。这些结果与肠上皮细胞基底外侧质膜中存在ATP依赖、钙调蛋白调节的钙转运机制一致，并表明钙调蛋白除了控制胞质钙水平外，还可能调节跨上皮钙吸收。
