Erdoğan S, Loğoğlu G, Ozgünen T
Cukurova University, School of Medicine, Department of Physiology, Adana, Turkey.
Gen Physiol Biophys. 1996 Oct;15(5):371-87.
Experiments were performed to identify the ionic basis of membrane potential changes in the Rana cameranoi egg, from prior to fertilization through the first cleavage. The membrane potential was monitored continuously during this period. Ten per cent Ringer was used as the recording solution in the control group. The effects of Na+ or Ca2+ conductances were observed by altering external concentrations of these ions. K+ and Cl- conductances were tested by adding channel blockers of these ions (TEA and SITS, respectively) to the extracellular medium. The resting potential of the unfertilized egg is mainly affected by K+ conductance. Chloride conductance is responsible for the depolarization phase of the fertilization potential evoked by sperm entry, and K+ conductance is responsible for the repolarization phase of this potential. We suggest that Na+ permeability does not directly contribute to the fertilization potential; however fertilization potential peak is significantly reduced upon a reduction of extracellular sodium. The fertilization potential is not significantly influenced by extracellular Ca2+, and eggs fertilized in calcium-free solutions maintain their normal development; these results suggest that extracellular Ca2+ does not significantly contribute to the electrical and mechanical blocks that prevent polyspermy. The membrane potential of the fertilized egg does not alter significantly until the first cleavage. Potassium conductance contributes to hyperpolarization generated upon the first cleavage, whereas sodium is the basic ion responsible for the phase which follows peak hyperpolarization, and which plays a role in the return of the post-cleavage membrane potential to a steady level. Cl- conductance, which is important as the ionic basis of the fertilization potential, does not significantly influence any parameter of the cleavage cycle.
进行了实验以确定泽氏蛙卵从受精前到第一次卵裂期间膜电位变化的离子基础。在此期间持续监测膜电位。对照组使用10%的林格氏液作为记录溶液。通过改变这些离子的外部浓度来观察Na⁺或Ca²⁺电导的影响。通过向细胞外培养基中添加这些离子的通道阻滞剂（分别为TEA和SITS）来测试K⁺和Cl⁻电导。未受精卵的静息电位主要受K⁺电导影响。Cl⁻电导负责精子进入诱发的受精电位的去极化阶段，而K⁺电导负责该电位的复极化阶段。我们认为Na⁺通透性并不直接促成受精电位；然而，细胞外钠减少时，受精电位峰值会显著降低。受精电位不受细胞外Ca²⁺的显著影响，在无钙溶液中受精的卵保持正常发育；这些结果表明细胞外Ca²⁺对防止多精入卵的电和机械屏障没有显著贡献。受精卵的膜电位在第一次卵裂前没有显著变化。K⁺电导促成第一次卵裂时产生的超极化，而Na⁺是超极化峰值后阶段的基本离子，在卵裂后膜电位恢复到稳定水平中起作用。作为受精电位离子基础很重要的Cl⁻电导，对卵裂周期的任何参数都没有显著影响。
