Physiological Study of the Mechanism Involved in Ca^<2+> Waves and Ca^<2+> Oscillations in Fertilized Mammalian Eggs

卵子受精时细胞内钙离子浓度（Ca）的增加触发卵子活化。哺乳动物受精卵表现出传播的钙波和重复的钙瞬态（钙振荡）。本研究旨在分析这些时空Ca信号产生的机制。精卵相互作用如何产生导致卵子中Ca反应的信号？仓鼠卵质膜上被认为介导精子-卵子粘附或结合的分子被它们的配体或抗体刺激，但没有Ca反应。酪氨酸激酶的抑制剂被认为与膜受体相关，但不能阻断精子诱导的钙反应。因此，表面分子信号产生的证据尚未获得，这使我们认为细胞质mic精子因子(S)引入卵子可能在精卵相互作用的信号转导中发挥更重要的作用。ip_4 -活化Ca内流…我们从生理上鉴定了肌醇1,3,4,5-四磷酸（IP_4）激活的仓鼠卵钙内流途径。钙内流提供钙重新填充内质网（ER），钙通过肌醇1,4,5-三磷酸（IP_3）的作用从内质网释放，引起钙的重复释放。我们利用激光共聚焦扫描显微镜（CLSM）观察到，在受精卵中Ca波在细胞质深处传播，细胞核中的Ca也比周围细胞质中的Ca增加。用注射的亲脂性荧光染料DiI对内质网进行染色，并用CLSM进行观察。内质网在卵细胞内呈网状分布，与IP_3受体的分布一致。在未成熟卵母细胞中，内质网和IP_3受体不均匀地分布在细胞核表面和周围。预注入笼状IP_3的光裂解诱导Ca释放主要发生在核区。这些发现表明，在卵母细胞成熟过程中，ER和IP_3受体的重新分配是获得正常受精能力的先决因素。少

An increase in intracellular calcium ion concentration (Ca) in eggs at fertilization triggers egg activation. Fertilized mammalian eggs show propagating Ca waves and repetitive Ca transients (Ca oscillations). The present study aimed to analyze the mechanism involved in the generation of these spatial and temporal Ca signals.1. How does sperm-egg interaction generate signals leading to Ca responses in eggs? Molecules on the hamster egg plasma membrane that are suggested to mediate sperm-egg adhesion or binding were stimulated by thier ligands or antibodies, but no Ca response was not. The inhibitors of tyrosin kinases which are supposed to be associated with the membrane receptors did not block sperm-induced Ca responses. Thus evidence for the signal genetation in surface molecules was not obtained, leading us to think that cytoplas mic sperm factor (S) introduced into the egg may play more important role in the signal transduction of sperm-egg interaction.2. IP_4-activatee Ca influx p … More athway. We physiologicaly identified inositol 1,3,4,5-tetrakis phosphate (IP_4)-activated Ca influx pathway in hamster eggs. The Ca influx provides Ca to refill the endoplasmic reticulum (ER) from which Ca has been released by the action of inositol 1,4,5-trisphosphate (IP_3), giving rise to repeated Ca release.3. We observed using a confocal laser scanning microscope (CLSM) that the Ca wave in the fertilized hamster egg propagates deep in the cytoplasm, and that Ca in the nucleus also increases comparably with that in the surrouding cytoplasm.4. The ER was stained by injected lipophilic fluorescent dye DiI and observed with CLSM.The ER was found to form a fine network throughout the egg, consistent with the distribution of IP_3 receptors. In immature oocytes the ER as well as IP_3 receptors was distributed inhomogeneously as dence patches in the surface area and aound the nucleus. Ca release induced by photocleavage of preinjected caged IP_3 occurred predominantly in the nuclear zone. These findings indicate that the redistribution of the ER and IP_3 receptors during oocyte maturation is a prerequisite factor for acquisition of the ability to undergo normal fertilization with the Ca waves. Less