Sepúlveda F V, Smith S M
Pflugers Arch. 1987 Mar;408(3):231-8. doi: 10.1007/BF02181464.
Intestinal epithelial cells isolated from rabbit small intestine and whose plasma membrane had been rendered highly permeable were used to study the role of intracellular structures in Ca2+ buffering. Monitoring free Ca2+ with a selective electrode revealed that the cells could reduce Ca2+ concentration in the medium to a level of 3.6 X 10(-7) M independently, within a certain range, of the initial Ca2+ concentration or amount of cells used. Ca2+ buffering by permeabilised enterocytes was Mg2+- and ATP-dependent and was abolished in the presence of the Ca2+ ionophore A23187. The rapidity of Ca2+ buffering, but not the final Ca2+ level attained, was reduced in the combined presence of the mitochondrial inhibitors azide and oligomycin or in the presence of ruthenium red. Buffering of Ca2+ was abolished in the presence of vanadate, although some uptake was still observed. Complete blocking occurred in the presence of both vanadate and mitochondrial inhibitors. Measurement of initial rates of uptake with radioactive calcium revealed that mitochondrial uptake plays a role at relatively high Ca concentrations but that at the presumably physiological levels most of the uptake is into a non-mitochondrial compartment. Non-differentiated crypt cells seemed to handle intracellular Ca2+ in a similar way as mature villus cells, although they appeared to buffer at a level about 2 X 10(-7) M lower.
从兔小肠分离出的肠上皮细胞，其质膜已具有高通透性，用于研究细胞内结构在钙缓冲中的作用。用选择性电极监测游离钙表明，细胞能够在一定范围内独立地将培养基中的钙浓度降低到3.6×10⁻⁷M的水平，这与初始钙浓度或所用细胞数量无关。通透的肠上皮细胞对钙的缓冲作用依赖于镁和ATP，并且在存在钙离子载体A23187时被消除。在同时存在线粒体抑制剂叠氮化物和寡霉素或存在钌红的情况下，钙缓冲的速度降低，但最终达到的钙水平不受影响。在存在钒酸盐的情况下，钙的缓冲作用被消除，尽管仍观察到一些摄取。在同时存在钒酸盐和线粒体抑制剂的情况下完全阻断。用放射性钙测量初始摄取速率表明，线粒体摄取在相对高的钙浓度下起作用，但在大概生理水平下，大部分摄取进入非线粒体区室。未分化的隐窝细胞处理细胞内钙的方式似乎与成熟的绒毛细胞相似，尽管它们的缓冲水平似乎低约2×10⁻⁷M。
