Location of ryanodine and dihydropyridine receptors in frog myocardium.
Location of ryanodine and dihydropyridine receptors in frog myocardium.
复制标题
青蛙心肌中兰尼碱和二氢吡啶受体的位置。
DOI：
10.1016/s0006-3495(03)74924-8
复制
发表时间：
2003
影响因子：
3.4
通讯作者：
Franzini-Armstrong,Clara
中科院分区：
文献类型：
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作者：
Tijskens,Pierre;Meissner,Gerhard;Franzini-Armstrong,Clara
青蛙心肌的逐次激活几乎完全依赖于钙从细胞外空间进入。心房肌在某些条件下还显示出内部钙释放，但心室中的内部释放不存在或非常低。我们利用放射性兰尼碱的结合、RyR和DHPR的免疫标记、以及薄片和冷冻断裂电子显微镜检查了青蛙心脏的两个心房和心室心肌中肌浆网（SR）钙释放通道（兰尼碱受体，RyRs）和表面膜钙通道（二氢吡啶受体，DHPRs）的含量和分布。在来自两种类型腔室的细胞中，SR 形成外周耦合，并且在两种腔室中，外周耦合与 DHPR 簇共定位。然而，尽管兰尼碱的低水平高亲和力结合是可检测到的，并且 RyR 存在于心房的外周耦合中，但心室基本上没有显示兰尼碱结合，并且通过电子显微镜或免疫标记都无法检测到 RyR。结果与心室内部钙释放的缺乏一致，并提出了在没有 RyR 的情况下 DHPR 在外周耦合中的重要性的问题。有趣的是，两个心室中的游离 SR 膜显示出代表 Ca2+ ATP 酶的膜内颗粒的密度较低但相等。
Frog myocardium depends almost entirely on calcium entry from extracellular spaces for its beat-to-beat activation. Atrial myocardium additionally shows internal calcium release under certain conditions, but internal release in the ventricle is absent or very low. We have examined the content and distribution of the sarcoplasmic reticulum (SR) calcium release channels (ryanodine receptors, RyRs) and the surface membrane calcium channels (dihydropyridine receptors, DHPRs) in myocardium from the two atria and the ventricle of the frog heart using binding of radioactive ryanodine, immunolabeling of RyR and DHPR, and thin section and freeze-fracture electron microscopy. In cells from both types of chambers, the SR forms peripheral couplings and in both chambers peripheral couplings colocalize with clusters of DHPRs. However, although a low level of high affinity binding of ryanodine is detectable and RyRs are present in peripheral couplings of the atrium, the ventricle shows essentially no ryanodine binding and RyRs are not detectable either by electron microscopy or immunolabeling. The results are consistent with the lack of internal calcium release in the ventricle, and raise questions regarding the significance of DHPR at peripheral couplings in the absence of RyR. Interestingly, the free SR membrane in both heart chambers shows a low but equal density of intramembrane particles representing the Ca2+ATPase.