SummaryMammalian sperm have to undergo capacitation to be fertilization competent. Capacitated sperm in vitro show hyperpolarization of the membrane potential. It has been reported that in mouse membrane hyperpolarization is necessary for the acrosome reaction. We recently found that the fluid of the hamster oviduct, where fertilization occurs, contained a high potassium (K+) concentration (~20 mEq/l). This high K+ concentration could depolarize the membrane potential and prevent the acrosome reaction/fertilization. Conversely, some beneficial effects on capacitation of high K+ concentration or a high K/Na ratio were also reported. In the present study, we investigated the effects of oviduct high K+ concentration on hamster sperm capacitation-associated events and fertilization. The present study confirmed that, in hamster sperm, membrane potential was hyperpolarized upon in vitro capacitation, indicating that capacitation-associated hyperpolarization is a universal phenomenon among mammalian species. An increase in KCl concentration in the medium to 20 mM significantly depolarized the membrane potential and suppressed hyperpolarization when in the presence of >101 mM NaCl. However, an increase in the KCl concentration to 20 mM did not significantly affect the percentage of motile sperm, hyperactivation or the acrosome reaction. No effect of 20 mM KCl on in vitro fertilization was observed. In addition, no correlative changes in hyperactivation and the acrosome reaction with K/Na ratio were observed. These results suggested that in hamsters the oviduct K+ concentration suppressed hyperpolarization but had no effect on capacitation and in vitro fertilization. Our results raised a question over the physiological significance of capacitation-associated hyperpolarization.

中文翻译：

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输卵管中高浓度的 K+ 可抑制超极化，但不能阻止仓鼠的超活化、顶体反应和体外受精

摘要哺乳动物精子必须经过获能才能受精。获能精子体外显示膜电位的超极化。据报道，在小鼠膜超极化是顶体反应所必需的。我们最近发现，受精发生的仓鼠输卵管的液体中含有高钾（K+) 浓度 (~20 mEq/l)。这个高K+浓度可以使膜电位去极化并阻止顶体反应/受精。相反，对高 K 的获能有一些有益影响+还报道了浓度或高 K / Na 比率。在本研究中，我们研究了输卵管高 K 的影响+专注于仓鼠精子获能相关事件和受精。本研究证实，在仓鼠精子中，膜电位在体外获能，表明与获能相关的超极化是哺乳动物物种中的普遍现象。当存在 >101 mM NaCl 时，培养基中 KCl 浓度增​​加到 20 mM 会显着使膜电位去极化并抑制超极化。然而，将 KCl 浓度增​​加到 20 mM 不会显着影响活动精子的百分比、过度活化或顶体反应。20 mM KCl 对体外观察到受精。此外，没有观察到过度活化和顶体反应与 K/Na 比的相关变化。这些结果表明，在仓鼠中，输卵管 K+浓度抑制超极化，但对容量没有影响体外施肥。我们的结果提出了一个关于获能相关超极化的生理意义的问题。