Herrmann-Frank A, Lehmann-Horn F
Department of Applied Physiology, University of Ulm, D-89069 Ulm, Germany.
Pflugers Arch. 1996 May;432(1):155-7. doi: 10.1007/s004240050117.
45Ca2+ flux and single channel measurements have related that the Ca2+ release channel/ryanodine receptor complex of striated muscle is regulated by micromolar cytoplasmic Ca2+. The effect of luminal Ca2+, however, remains controversial. In the experiments presented here, we reconstituted the isolated Ca2+ release channel of rabbit skeletal muscle sarcoplasmic reticulum into planar lipid bilayers in the presence of symmetrical K+ solutions. Using K+ as the charge carrier, we were able to examine the effect of changes in luminal calcium in the micro- to millimolar range. In the presence of activating cytoplasmic Ca2+, the release channel was activated and inactivated in a concentration-dependent manner by luminal Ca2+. Since increasing cytoplasmic EGTA concentrations shifted the dependence of channel open probability on luminal Ca2+ to higher Ca2+ concentrations, it is suggested that luminal Ca2+ exerts ist regulating effect by acting on Ca2+ binding sites accessible from the cytoplasmic side of the channel.
45Ca2+通量和单通道测量结果表明，横纹肌的Ca2+释放通道/雷诺丁受体复合物受微摩尔浓度的细胞质Ca2+调节。然而，管腔Ca2+的作用仍存在争议。在本文所呈现的实验中，我们将兔骨骼肌肌浆网分离出的Ca2+释放通道重构到存在对称K+溶液的平面脂质双分子层中。使用K+作为电荷载体，我们能够检测微摩尔至毫摩尔范围内管腔钙变化的影响。在激活细胞质Ca2+存在的情况下，释放通道被管腔Ca2+以浓度依赖的方式激活和失活。由于增加细胞质EGTA浓度会使通道开放概率对管腔Ca2+的依赖性向更高的Ca2+浓度转移，因此表明管腔Ca2+通过作用于通道细胞质侧可及的Ca2+结合位点发挥其调节作用。
