Tripathy A, Xu L, Pasek D A, Meissner G
Departments of Biochemistry and Biophysics, and Physiology, University of North Carolina, Chapel Hill, NC 27599-7260, USA.
J Membr Biol. 1999 Jun 1;169(3):189-98. doi: 10.1007/s002329900530.
Single channel and [3H]ryanodine binding measurements were performed to test for a direct functional interaction between 2,3-butanedione 2-monoxime (BDM) and the skeletal and cardiac muscle sarcoplasmic reticulum Ca2+ release channels (ryanodine receptors). Single channel measurements were carried out in symmetric 0.25 m KCl media using the planar lipid bilayer method. BDM (1-10 mm) activated suboptimally Ca2+-activated (0.5-1 microM free Ca2+) single, purified and native cardiac and skeletal release channels in a concentration-dependent manner by increasing the number of channel events without a change of single channel conductances. BDM activated the two channel isoforms when added to either side of the bilayer. At a maximally activating cytosolic Ca2+ concentration of 20 microM, BDM was without effect on the cardiac channel, whereas it inhibited skeletal channel activities with IC50 approximately 2.5 mm. In agreement with single channel measurements, high-affinity [3H]ryanodine binding to the two channel isoforms was increased in a concentration-dependent manner at </=1 microM Ca2+. BDM was without a noticeable effect at low (</=0.01 microM) Ca2+ concentrations. At 20 microM Ca2+, BDM inhibited the skeletal but not cardiac channel. These results suggest that BDM regulates the Ca2+ release channels from the sarcoplasmic reticulum of skeletal and cardiac muscle in a concentration, Ca2+ and tissue-dependent manner.
进行单通道和[3H]ryanodine结合测量，以测试2,3 - 丁二酮单肟（BDM）与骨骼肌和心肌肌浆网Ca2+释放通道（ryanodine受体）之间是否存在直接功能相互作用。使用平面脂质双层法在对称的0.25 m KCl介质中进行单通道测量。BDM（1 - 10 mM）以浓度依赖性方式，通过增加通道事件数量而不改变单通道电导，次优激活Ca2+激活的（0.5 - 1 microM游离Ca2+）纯化和天然的心脏及骨骼肌释放通道。当BDM添加到双层的任一侧时，均可激活这两种通道亚型。在最大激活的胞质Ca2+浓度为20 microM时，BDM对心脏通道无影响，而对骨骼肌通道活性有抑制作用，IC50约为2.5 mM。与单通道测量结果一致，在Ca2+浓度≤1 microM时，高亲和力的[3H]ryanodine与两种通道亚型的结合以浓度依赖性方式增加。在低（≤0.01 microM）Ca2+浓度下，BDM无明显影响。在20 microM Ca2+时，BDM抑制骨骼肌通道而非心脏通道。这些结果表明，BDM以浓度、Ca2+和组织依赖性方式调节骨骼肌和心肌肌浆网的Ca2+释放通道。
