Inositol 1,4,5,-triphosphate activated Calcium Channels in oocytes.

在受精过程中，海胆卵细胞内钙浓度会短暂升高。肌醇1,4,5，-三磷酸（IP_3）被认为是激活细胞内钙储存通道并引起钙瞬态的第二信使。然而，没有直接证据表明这种ip_3激活的钙通道在海胆卵中存在。这些实验旨在表明证据。IP_3引起未受精卵微粒体部分瞬间释放Ca^<2+>。应用肝素（1mg /ml）抑制释放。此外，我们还发现咖啡因也能引起微粒体部分Ca^<2+>的瞬时释放，并呈剂量依赖性。肝素没有阻断释放。这意味着咖啡因引起钙释放的机制与ip_3诱导的钙释放不同。我们尝试测量通过ip_3诱导的Ca释放通道的电流。检查了融合平面双层膜的微粒体膜的单通道记录。发现了多种Ca^<2+>、K^+和Cl^-通道，但未观察到ip_3诱导的Ca通道。另一种证明IP_3诱导Ca释放通道存在的方法必须是从微粒体部分中纯化“IP_3受体”。获得了约200 KD的IP_3结合蛋白。目前正在研究将蛋白质重组成人工膜的方法。

A transient increase in intracellular calcium concentration occurs in sea urchin eggs during fertilization. Inositol 1,4,5,-triphosphate(IP_3) is thought to be the second messenger which activates calcium channels of intracellular store and to cause the Ca-transient. However, there is no direct evidence for such a IP_3-activated Ca channel in sea urchin eggs. These experiments aimed to show the evidences.1. IP_3 caused a transient release of Ca^<2+> from microsomal fraction of unfertililized eggs. The release was inhibited by the application of heparin (1 mg/ml). We found in addition, that caffein also caused a transient release of Ca^<2+> from the microsomal fraction in dose dependent manner. Heparin did not block the release. This means that caffeine causes a Ca release via a different mechanism from the IP_3-induced Ca release.2. We tried to measured the current passing a IP_3-induced Ca releasing channel. Single channel recordings of the microsomal membrane which fused with a planar bilayer membrane were examined. Several kinds of Ca^<2+>, K^+ and Cl^- channels were found but no IP_3-induced Ca channel was observed.3. Another approach to show the existence of IP_3- induced Ca releasing channel must be the purification of "IP_3-receptors" from the microsomal fraction. IP_3 binding proteins of about 200 KD were obtained. The reconstitution of the protein into an artificial membrane is now examining.