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

受精时卵细胞内钙离子浓度的增加会触发卵子的激活。哺乳动物受精卵表现出传播的钙波和重复的钙瞬变(钙振荡)。本研究旨在分析这些空间和时间钙信号的产生机制。精子-卵子相互作用如何产生信号，导致卵子中的钙反应？金黄地鼠卵质膜上可能参与精卵黏附或结合的分子可被其配体或抗体所刺激，而NO-Ca反应则不能。酪氨酸激酶的抑制剂被认为与膜受体有关，但不能阻止精子诱导的钙反应。因此，没有获得表面分子中信号发生的证据，这使得我们认为引入卵子中的细胞质精子因子(S)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-激活者钙内流p…更多的地铁。我们在生理学上鉴定了1，3，4，5-磷酸四氢肌醇(IP_4)激活的仓鼠卵钙内流途径。钙的内流为内质网(ER)提供了钙，内质网中的钙通过1，4，5-三磷酸(IP_3)的作用从内质网中释放出来，导致钙的反复释放。用激光共聚焦扫描显微镜(CLSM)观察到，受精卵中的钙波在细胞质深处传播，细胞核中的钙也与周围细胞质中的钙相对应地增加。用注射的亲脂荧光染料DII对内质网进行染色，并用CLSM进行观察，发现内质网在整个卵子中形成一个细小的网络，与IP_3受体的分布一致。在未成熟卵母细胞中，ER和IP_3受体在卵母细胞表面区和核周呈不均匀的斑块分布。预先注射的笼状IP_3光裂解引起的CA释放主要发生在核区。这些结果表明，卵母细胞成熟过程中ER和IP3受体的重新分布是获得正常受精能力的先决条件。较少

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