海胆卵中的钠钾交换。I. 受精时的动力学和生化特性

Sodium-potassium exchange in sea urchin egg. I. Kinetic and biochemical characterization at fertilization.

作者信息

Ciapa B, De Renzis G, Girard J P, Payan P

出版信息

J Cell Physiol. 1984 Oct;121(1):235-42. doi: 10.1002/jcp.1041210129.

Abstract

Biochemical and kinetic characteristics of the Na+-K+ exchange were studied in Paracentrotus lividus eggs. Measurement of the 86Rb uptake shows that ouabain-sensitive 86Rb uptake is dramatically stimulated within the first minute following fertilization. The Na+-K+ pump-mediated K+ entry presents a maximal rate at 8 min postfertilization and then decreases to reach a plateau within 30 min. We assess that the steep rise in cell K+ occurring at fertilization (J.P. Girard, P. Payan, C. Sardet, Exp. Cell. Res. 142:215-221, 1982) does not originate from a net entry of external K+. Measured 30 min postfertilization, the half-maximal activation by K+ of the ouabain-sensitive Na+-K+ exchange is 5-6 mM and the ouabain IC50 is 5.10(-5) M. Egg cortices from unfertilized and fertilized eggs show comparable Na+-K+ ATPase activity with a 50% ouabain-sensitive fraction. Vm and Km for Na+ and K+ of the enzyme are of the same order of magnitude in cortices of unfertilized and fertilized eggs. Cortical Na+-K+ ATPase from unfertilized eggs shows a ten fold increase of activity between pH 6.7 and pH 7.7. The results strongly suggest that the plasma membrane of unfertilized eggs contains a preexisting Na+-K+ transporting system which is obligatorily stimulated at fertilization.

摘要

在紫海胆卵中研究了Na⁺-K⁺交换的生化和动力学特性。对⁸⁶Rb摄取的测量表明，哇巴因敏感的⁸⁶Rb摄取在受精后的第一分钟内受到显著刺激。Na⁺-K⁺泵介导的K⁺进入在受精后8分钟达到最大速率，然后下降并在30分钟内达到平台期。我们评估受精时细胞内K⁺的急剧增加（J.P. Girard、P. Payan、C. Sardet，《实验细胞研究》142:215 - 221，1982）并非源于外部K⁺的净进入。在受精后30分钟测量，哇巴因敏感的Na⁺-K⁺交换对K⁺的半最大激活浓度为5 - 6 mM，哇巴因的IC50为5×10⁻⁵ M。未受精卵和受精卵的卵皮质显示出相当的Na⁺-K⁺ ATP酶活性，其中50%对哇巴因敏感。未受精卵和受精卵皮质中该酶对Na⁺和K⁺的Vm和Km处于相同数量级。未受精卵的皮质Na⁺-K⁺ ATP酶在pH 6.7至pH 7.7之间活性增加了10倍。结果强烈表明，未受精卵的质膜含有一个预先存在的Na⁺-K⁺转运系统，该系统在受精时必然受到刺激。