Deng M Q, Huang X Y, Tang T S, Sun F Z
Institute of Developmental Biology, Chinese Academy of Sciences, Beijing, People's Republic of China.
Biol Reprod. 1998 Mar;58(3):807-13. doi: 10.1095/biolreprod58.3.807.
Mouse germinal vesicle (GV)-stage oocytes not only show Ca2+ oscillations in response to fertilization but also exhibit spontaneous Ca2+ oscillations during meiotic maturation in vitro. Spontaneous Ca2+ oscillations were entirely suppressed by microinjection of heparin (25 microM final intracellular concentration), an antagonist of inositol trisphosphate (IP3) receptor, whereas fertilization-induced Ca2+ oscillations were only partially inhibited by heparin even at a high dosage of 600 microM. Inhibition of endogenous IP3 generation by antagonizing phospholipase C using U73122 (20 microM final concentration) also failed to suppress the generation of fertilization-induced Ca2+ transients, suggesting that the two types of Ca2+ oscillations do not have the same dependence on IP3-induced Ca2+ release. In addition, spontaneous Ca2+ oscillations require the presence of intact GV whereas fertilization-induced Ca2+ oscillations are independent of the GV but require cytoplasm, since enucleation eliminated only spontaneous Ca2+ oscillations but not fertilization-induced Ca2+ oscillations. These results suggest that IP3-induced Ca2+ release is the primary mechanism responsible for spontaneous Ca2+ oscillations. Sperm-induced Ca2+ oscillations, however, may employ more complex mechanisms during fertilization.
小鼠生发泡（GV）期卵母细胞不仅在受精时会出现钙离子振荡，而且在体外减数分裂成熟过程中也会表现出自发性钙离子振荡。通过显微注射肝素（最终细胞内浓度为25微摩尔）完全抑制了自发性钙离子振荡，肝素是肌醇三磷酸（IP3）受体的拮抗剂，而即使在600微摩尔的高剂量下，肝素对受精诱导的钙离子振荡也只是部分抑制。使用U73122（最终浓度为20微摩尔）拮抗磷脂酶C来抑制内源性IP3生成，同样未能抑制受精诱导的钙离子瞬变的产生，这表明这两种类型的钙离子振荡对IP3诱导的钙离子释放的依赖性不同。此外，自发性钙离子振荡需要完整的生发泡存在，而受精诱导的钙离子振荡不依赖于生发泡，但需要细胞质，因为去核仅消除了自发性钙离子振荡，而没有消除受精诱导的钙离子振荡。这些结果表明，IP3诱导的钙离子释放是自发性钙离子振荡的主要机制。然而，精子诱导的钙离子振荡在受精过程中可能采用更复杂的机制。
