Animal Physiology and Evolution Laboratory, Stazione Zoologica Anton Dohrn, Napoli, Italy.
PLoS One. 2013;8(1):e54604. doi: 10.1371/journal.pone.0054604. Epub 2013 Jan 22.
Voltage-dependent calcium currents play a fundamental role during oocyte maturation, mostly L-type calcium currents, whereas T-type calcium currents are involved in sperm physiology and cell growth. In this paper, using an electrophysiological and pharmacological approach, we demonstrated, for the first time in oocytes, that T-type calcium currents are present with functional consequences on the plasma membrane of growing immature oocytes of the ascidian Styela plicata. We classified three subtypes of immature oocytes at the germinal vesicle stage on the basis of their size, morphology and accessory cellular structures. These stages were clearly associated with an increased activity of T-type calcium currents and hyperpolarization of the plasma membrane. We also observed that T-type calcium currents oscillate in the post-fertilization embryonic stages, with minimal amplitude of the currents in the zygote and maximal at 8-cell stage. In addition, chemical inhibition of T-type calcium currents, obtained by applying specific antagonists, induced a significant reduction in the rate of cleavage and absence of larval formation. We suggest that calcium entry via T-type calcium channels may act as a potential pacemaker in regulating cytosolic calcium involved in fertilization and early developmental events.
电压门控钙电流在卵母细胞成熟过程中起着至关重要的作用，主要是 L 型钙电流，而 T 型钙电流则参与精子生理和细胞生长。在本文中，我们首次在海鞘 Styela plicata 的生长未成熟卵母细胞的质膜上证明了 T 型钙电流的存在及其功能意义，使用了电生理学和药理学方法。我们根据其大小、形态和附属细胞结构将处于生发泡阶段的未成熟卵母细胞分为三个亚型。这些阶段与 T 型钙电流活性的增加和质膜的超极化明显相关。我们还观察到 T 型钙电流在受精后的胚胎阶段呈振荡状态，在受精卵中电流幅度最小，在 8 细胞阶段最大。此外，通过应用特定的拮抗剂抑制 T 型钙电流会导致卵裂率显著降低，并且幼虫形成缺失。我们认为，通过 T 型钙通道的钙内流可能作为调节与受精和早期发育事件相关的胞质钙的潜在起搏器发挥作用。
