Cardiovascular Research Centre CSIC and IIB Sant Pau, Hospital de Sant Pau, Barcelona, Barcelona, Spain.
PLoS One. 2011;6(8):e23708. doi: 10.1371/journal.pone.0023708. Epub 2011 Aug 29.
Calcium release from the sarcoplasmic reticulum (SR) plays a central role in the regulation of cardiac contraction and rhythm in mammals and humans but its role is controversial in teleosts. Since the zebrafish is an emerging model for studies of cardiovascular function and regeneration we here sought to determine if basic features of SR calcium release are phylogenetically conserved. Confocal calcium imaging was used to detect spontaneous calcium release (calcium sparks and waves) from the SR. Calcium sparks were detected in 16 of 38 trout atrial myocytes and 6 of 15 ventricular cells. The spark amplitude was 1.45±0.03 times the baseline fluorescence and the time to half maximal decay of sparks was 27±3 ms. Spark frequency was 0.88 sparks µm(-1) min(-1) while calcium waves were 8.5 times less frequent. Inhibition of SR calcium uptake reduced the calcium transient (F/F(0)) from 1.77±0.17 to 1.12±0.18 (p = 0.002) and abolished calcium sparks and waves. Moreover, elevation of extracellular calcium from 2 to 10 mM promoted early and delayed afterdepolarizations (from 0.6±0.3 min(-1) to 8.1±2.0 min(-1), p = 0.001), demonstrating the ability of SR calcium release to induce afterdepolarizations in the trout heart. Calcium sparks of similar width and duration were also observed in zebrafish ventricular myocytes. In conclusion, this is the first study to consistently report calcium sparks in teleosts and demonstrate that the basic features of calcium release through the ryanodine receptor are conserved, suggesting that teleost cardiac myocytes is a relevant model to study the functional impact of abnormal SR function.
肌浆网（SR）中的钙离子释放对哺乳动物和人类的心脏收缩和节律调节起着核心作用，但在硬骨鱼中其作用存在争议。由于斑马鱼是心血管功能和再生研究的新兴模型，我们在此试图确定 SR 钙离子释放的基本特征是否在进化上得到保守。使用共聚焦钙成像来检测 SR 中的自发钙离子释放（钙火花和钙波）。在 38 个鳟鱼心房肌细胞和 15 个心室细胞中，检测到钙火花。火花幅度是基线荧光的 1.45±0.03 倍，火花衰减到一半的时间为 27±3ms。火花频率为 0.88 个火花µm(-1) min(-1)，而钙波的频率则低 8.5 倍。抑制 SR 钙摄取使钙瞬变（F/F(0)）从 1.77±0.17 降低到 1.12±0.18（p=0.002），并消除了钙火花和钙波。此外，将细胞外钙从 2mM 升高到 10mM 会促进早期和延迟后的去极化（从 0.6±0.3 min(-1) 增加到 8.1±2.0 min(-1)，p=0.001），表明 SR 钙离子释放能够在鳟鱼心脏中引发后去极化。在斑马鱼心室肌细胞中也观察到了类似宽度和持续时间的钙火花。总之，这是首次在硬骨鱼中一致报道钙火花的研究，并证明通过兰尼碱受体释放钙离子的基本特征是保守的，这表明硬骨鱼心肌细胞是研究异常 SR 功能对心脏功能影响的相关模型。
