Abramson J J, Zable A C, Favero T G, Salama G
Department of Physics, Portland State University, Oregon 92707, USA.
J Biol Chem. 1995 Dec 15;270(50):29644-7. doi: 10.1074/jbc.270.50.29644.
The thiol-oxidizing reagent, thimerosal, has been shown to increase the intracellular Ca2+ concentration, to induce Ca2+ spikes in several cell types, and to increase the sensitivity of intracellular Ca2+ stores to inositol 1,4,5-trisphosphate. Ryanodine-sensitive stores have also been implicated in the generation of Ca2+ oscillations induced by the addition of thimerosal. Here we report that micromolar concentrations of thimerosal stimulate Ca2+ release from skeletal muscle sarcoplasmic reticulum vesicles, inhibit high affinity [3H]ryanodine binding, and modify the channel activity of the reconstituted Ca2+ release protein. Thimerosal inhibits ryanodine binding by decreasing the binding capacity (Bmax) but does not affect the binding affinity or the dissociation rate of bound ryanodine. Single channel reconstitution experiments show that thimerosal (100-200 microM) stimulates single channel activity without modifying channel conductance. The thimerosal-stimulated channel is not inhibited by heparin. Furthermore, a Ca(2+)-stimulated channel is first activated and then inhibited in a time-dependent fashion by high concentrations of thimerosal (1 mM). Once inactivated, the channel cannot be reactivated by addition of either Ca2+ or ATP.
硫醇氧化试剂硫柳汞已被证明可增加细胞内钙离子浓度，在多种细胞类型中诱导钙离子尖峰，并增加细胞内钙离子储存对肌醇1,4,5 -三磷酸的敏感性。对兰尼碱敏感的储存也与添加硫柳汞诱导的钙离子振荡的产生有关。在此我们报告，微摩尔浓度的硫柳汞可刺激骨骼肌肌浆网囊泡释放钙离子，抑制高亲和力的[³H]兰尼碱结合，并改变重组钙离子释放蛋白的通道活性。硫柳汞通过降低结合容量（Bmax）来抑制兰尼碱结合，但不影响结合亲和力或结合兰尼碱的解离速率。单通道重组实验表明，硫柳汞（100 - 200微摩尔）可刺激单通道活性而不改变通道电导。硫柳汞刺激的通道不受肝素抑制。此外，高浓度的硫柳汞（1毫摩尔）可使钙离子刺激的通道先被激活，然后随时间呈依赖性抑制。一旦失活，该通道不能通过添加钙离子或ATP重新激活。
