Ryanodine activation and inhibition of the Ca2+ release channel of sarcoplasmic reticulum.
Ryanodine activation and inhibition of the Ca2+ release channel of sarcoplasmic reticulum.
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发表时间：
1986-05
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通讯作者：
G. Meissner
中科院分区：
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作者：
G. Meissner
通过测定在存在或不存在ryanodine的情况下被动负载45 Ca 2+的“重”囊泡的Ca 2+渗透性，研究了植物生物碱ryanodine对骨骼肌肌浆网Ca 2+释放通道的影响。根据实验条件，ryanodine刺激或抑制Ca 2+外流。囊泡被赋予渗透45 Ca 2+在ryanodine浓度为0.01 μ M时，稀释到含有两个Ca 2+释放通道抑制剂Mg 2+和钌红的介质。在ryanodine浓度大于10 μ M，45 Ca 2+流出抑制通道激活（5 μ M Ca 2+）或抑制（10 mM Mg 2+加10 μ M钌红）媒体。当囊泡与兰尼定在37 ℃和导致通道部分开放的介质中孵育时，观察到最佳的刺激效果。使用能够快速45 Ca 2+流出的心肌肌浆网囊泡获得了与上述结果相似的结果。使用缓慢渗透的分子L-[3 H]葡萄糖允许测量通道介导的流出率从囊泡在兰尼定的存在和不存在。在低激活浓度下，ryanodine没有明显改变外部Ca 2+，Mg 2+和腺嘌呤核苷酸对L-葡萄糖流出率的调节。这些结果提示了兰尼碱的两种可能的作用模式：1）通道门控机制的变化，这是使用缓慢渗透的分子L-葡萄糖不易检测到的;或2）通道结构的变化，这阻止了通道的完全关闭。
The effect of the plant alkaloid ryanodine on the skeletal muscle sarcoplasmic reticulum Ca2+ release channel was studied by determining the Ca2+ permeability of "heavy" vesicles passively loaded with 45Ca2+ in the presence or absence of ryanodine. Depending on the experimental conditions, ryanodine either stimulated or inhibited Ca2+ efflux. Vesicles were rendered permeable to 45Ca2+ at a ryanodine concentration of 0.01 microM when diluted into a medium containing the two Ca2+ release channel inhibitors Mg2+ and ruthenium red. At ryanodine concentrations greater than 10 microM, 45Ca2+ efflux was inhibited in channel-activating (5 microM Ca2+) or -inhibiting (10 mM Mg2+ plus 10 microM ruthenium red) media. An optimal stimulatory effect was observed when vesicles were incubated with ryanodine at 37 degrees C and in media that caused partial opening of the channel. Similar results to those described above were obtained using cardiac sarcoplasmic reticulum vesicles that were capable of rapid 45Ca2+ efflux. Use of the slowly permeating molecule L-[3H]glucose allowed measurement of channel-mediated efflux rates from vesicles in the presence and absence of ryanodine. At low activating concentrations, ryanodine did not appreciably change the regulation of L-glucose efflux rates by external Ca2+, Mg2+, and adenine nucleotide. These results suggested two possible modes of action of ryanodine: 1) a change in the gating mechanism of the channel which is not readily detected using the slowly permeating molecule L-glucose or 2) a change in channel structure which prevents its complete closing.