Egg activation at fertilization in mouse eggs is caused by a series of cytosolic Ca2+ oscillations that are associated with an increase in ATP concentrations driven by increased mitochondrial activity. We have investigated the role of Ca2+ oscillations in these changes in ATP at fertilization by measuring the dynamics of ATP and Ca2+ in mouse eggs. An initial ATP increase started with the first Ca2+ transient at fertilization and then a secondary increase in ATP occurred ∼1 h later and this preceded a small and temporary increase in the frequency of Ca2+ oscillations. Other stimuli that caused Ca2+ oscillations such as PLCz1 or thimerosal, caused smaller or slower changes in ATP that failed to show the distinct secondary rise. Sperm-induced Ca2+ oscillations in the egg also triggered changes in the fluorescence of NADH which followed the pattern of Ca2+ spikes in a similar pattern to oscillations triggered by PLCz1 or thimerosal. When eggs were loaded with low concentrations of the Ca2+ chelator BAPTA, sperm triggered one small Ca2+ increase, but there were still extra phases of ATP increase that were similar to control fertilized eggs. Singular Ca2+ increases caused by thapsigargin were much less effective in elevating ATP levels. Together these data suggest that the secondary ATP increase at fertilization in mouse eggs is not caused by increases in cytosolic Ca2+. The fertilizing sperm may stimulate ATP production in eggs via both Ca2+ and by another mechanism that is independent of PLCz1 or Ca2+ oscillations.

中文翻译：

---

精子诱导小鼠卵子中 ATP 水平二次增加，且与 Ca2+ 振荡无关

小鼠卵子受精时的卵子激活是由一系列胞质 Ca2+ 振荡引起的，这些振荡与线粒体活性增加所驱动的 ATP 浓度增加有关。我们通过测量小鼠卵子中 ATP 和 Ca2+ 的动态，研究了 Ca2+ 振荡在受精时 ATP 变化中的作用。最初的 ATP 增加始于受精时的第一次 Ca2+ 瞬变，然后约 1 h 后发生 ATP 的二次增加，这先于 Ca2+ 振荡频率的小幅暂时增加。其他引起 Ca2+ 振荡的刺激，如 PLCz1 或硫柳汞，引起 ATP 变化较小或较慢，未能显示出明显的二次上升。精子诱导的卵子中的 Ca2+ 振荡也会引发 NADH 荧光的变化，其遵循 Ca2+ 尖峰模式，其模式与 PLCz1 或硫柳汞触发的振荡类似。当卵子装载低浓度的 Ca2+ 螯合剂 BAPTA 时，精子会引发一小段 Ca2+ 增加，但仍然存在与对照受精卵类似的 ATP 增加的额外阶段。毒胡萝卜素引起的单一 Ca2+ 增加在提高 ATP 水平方面的效果要差得多。这些数据共同表明，小鼠卵子受精时次级 ATP 的增加并不是由胞质 Ca2+ 的增加引起的。受精精子可能通过 Ca2+ 和另一种独立于 PLCz1 或 Ca2+ 振荡的机制刺激卵子中 ATP 的产生。