Carey M B, Matsumoto S G
Department of Biological Structure and Function, Oregon Health Sciences University, School of Dentistry, 611 SW Campus Drive, Portland, OR, USA.
Brain Res. 2000 Apr 17;862(1-2):201-10. doi: 10.1016/s0006-8993(00)02128-4.
In a previous study we have shown that cultured neural crest cells exhibit spontaneous calcium transients and that these events are required for neurogenesis. In this study, we examine the mechanism that generates these calcium transients. Extracellular Ca(2+) modulates calcium transient activity. Lanthanum (La(3+)), a general calcium channel antagonist and zero extracellular Ca(2+), reduces the percentage of cells exhibiting calcium transients (26.2 and 40. 5%, respectively) and decreases calcium spiking frequency (4.5 to 1. 0 and 2.5 to 1.0 spikes/30 min, respectively). Intracellular calcium stores also contribute to the generation of calcium transients. Depleting the calcium stores of the endoplasmic reticulum (ER) reduces the percentage of active cells (15.7%) and calcium spiking frequency (2.8 to 1.5 spikes/30 min). Ryanodine (100 microM), which blocks calcium release regulated by the ryanodine receptor (RyR), had no effect on calcium transient activity. Blocking inositol 1,4, 5-triphosphate receptor (IP(3)R)-dependent calcium release, with elevated extracellular Mg(2+) (20 mM), abolished calcium transient activity. Mg(2+) did not block caffeine-sensitive calcium release (RyR-dependent) or voltage dependent calcium channels. Mg(2+) also suppressed thimerosal-induced calcium oscillations (IP(3)R-dependent). Small increases in the intracellular calcium concentration (Ca(2+)), increases the percentage of active cells and the calcium spiking frequency, while larger increases in Ca(2+) block the transients. Reducing intracellular IP(3) levels reduces the percentage of active cells and the calcium spiking frequency. We conclude that the mechanism for generating spontaneous calcium transients in cultured neural crest cells fits the model for IP(3)R-dependent calcium excitability of the ER.
在之前的一项研究中，我们已经表明，培养的神经嵴细胞表现出自发性钙瞬变，并且这些事件是神经发生所必需的。在本研究中，我们研究了产生这些钙瞬变的机制。细胞外Ca(2+)调节钙瞬变活性。镧（La(3+)），一种通用的钙通道拮抗剂，以及零细胞外Ca(2+)，降低了表现出钙瞬变的细胞百分比（分别为26.2%和40.5%），并降低了钙尖峰频率（分别从4.5降至1.0和从2.5降至1.0次尖峰/30分钟）。细胞内钙库也有助于钙瞬变的产生。耗尽内质网（ER）的钙库会降低活跃细胞的百分比（15.7%）和钙尖峰频率（从2.8降至1.5次尖峰/30分钟）。ryanodine（100 microM），它阻断由ryanodine受体（RyR）调节的钙释放，对钙瞬变活性没有影响。用升高的细胞外Mg(2+)（20 mM）阻断依赖肌醇1,4,5-三磷酸受体（IP(3)R）的钙释放，消除了钙瞬变活性。Mg(2+)没有阻断咖啡因敏感的钙释放（依赖RyR）或电压依赖性钙通道。Mg(2+)也抑制了硫柳汞诱导的钙振荡（依赖IP(3)R）。细胞内钙浓度（Ca(2+)）的小幅增加会增加活跃细胞的百分比和钙尖峰频率，而Ca(2+)的较大增加则会阻断瞬变。降低细胞内IP(3)水平会降低活跃细胞的百分比和钙尖峰频率。我们得出结论，培养的神经嵴细胞中产生自发性钙瞬变的机制符合ER依赖IP(3)R的钙兴奋性模型。
