Crossley I, Swann K, Chambers E, Whitaker M
Department of Physiology, University College London, U.K.
Biochem J. 1988 May 15;252(1):257-62. doi: 10.1042/bj2520257.
We investigated the contribution of external calcium ions to inositol phosphate-induced exocytosis in sea urchin eggs. We show that: (a) inositol phosphates activate eggs of the sea urchin species Lytechinus pictus and Lytechinus variegatus independently of external calcium ions; (b) the magnitude and duration of the inositol phosphate induced calcium changes are independent of external calcium; (c) in calcium-free seawater, increasing the volume of inositol trisphosphate solution injected decreased the extent of egg activation; (d) eggs in calcium-free sea water are more easily damaged by microinjection; microinjection of larger volumes increased leakage from eggs pre-loaded with fluorescent dye. We conclude that inositol phosphates do not require external calcium ions to activate sea urchin eggs. This is entirely consistent with their role as internal messengers at fertilization. The increased damage caused to eggs in calcium-free seawater injected with large volumes may allow the EGTA present in the seawater to enter the egg and chelate any calcium released by the inositol phosphates. This may explain the discrepancy between this and earlier reports.
我们研究了外部钙离子对海胆卵中肌醇磷酸诱导的胞吐作用的贡献。我们发现：（a）肌醇磷酸可独立于外部钙离子激活海胆物种 Lytechinus pictus 和 Lytechinus variegatus 的卵；（b）肌醇磷酸诱导的钙变化的幅度和持续时间与外部钙无关；（c）在无钙海水中，增加注射的三磷酸肌醇溶液的体积会降低卵激活的程度；（d）无钙海水中的卵更容易因显微注射而受损；注射更大体积会增加预先加载荧光染料的卵的渗漏。我们得出结论，肌醇磷酸不需要外部钙离子来激活海胆卵。这与它们在受精时作为内部信使的作用完全一致。向无钙海水中注射大量物质对卵造成的更大损伤可能会使海水中存在的乙二醇双四乙酸（EGTA）进入卵并螯合肌醇磷酸释放的任何钙。这可能解释了本研究与早期报告之间的差异。
