Institute of Life Science and School of Life Science, Nanchang University, Nanchang 330031, Jiangxi, China.
Institute of Reproductive Medicine, School of Medicine, Nantong University, Nantong 226019, Jiangsu, China.
Int J Mol Sci. 2021 Feb 5;22(4):1612. doi: 10.3390/ijms22041612.
Sperm-specific K ion channel (KSper) and Ca ion channel (CatSper), whose elimination causes male infertility in mice, determine the membrane potential and Ca influx, respectively. KSper and CatSper can be activated by cytosolic alkalization, which occurs during sperm going through the alkaline environment of the female reproductive tract. However, which intracellular pH (pH) regulator functionally couples to the activation of KSper/CatSper remains obscure. Although Na/H exchangers (NHEs) have been implicated to mediate pH in sperm, there is a lack of direct evidence confirming the functional coupling between NHEs and KSper/CatSper. Here, 5-(N, N-dimethyl)-amiloride (DMA), an NHEs inhibitor that firstly proved not to affect KSper/CatSper directly, was chosen to examine NHEs function on KSper/CatSper in mouse sperm. The results of patch clamping recordings showed that, when extracellular pH was at the physiological level of 7.4, DMA application caused KSper inhibition and the depolarization of membrane potential when pipette solutions were not pH-buffered. In contrast, these effects were minimized when pipette solutions were pH-buffered, indicating that they solely resulted from pH acidification caused by NHEs inhibition. Similarly, DMA treatment reduced CatSper current and intracellular Ca, effects also dependent on the buffer capacity of pH in pipette solutions. The impairment of sperm motility was also observed after DMA incubation. These results manifested that NHEs activity is coupled to the activation of KSper/CatSper under physiological conditions.
精子特异性钾离子通道 (KSper) 和钙离子通道 (CatSper)，其缺失会导致小鼠不育，分别决定了膜电位和钙离子内流。KSper 和 CatSper 可以被细胞质碱化激活，这种情况发生在精子通过女性生殖道的碱性环境时。然而，哪种细胞内 pH（pH）调节剂能与 KSper/CatSper 的激活功能偶联仍不清楚。尽管已经有研究表明钠/氢交换器（NHEs）介导精子中的 pH 值，但缺乏直接证据证实 NHEs 与 KSper/CatSper 之间的功能偶联。在这里，选择 5-（N，N-二甲基）-阿米洛利（DMA），一种最初被证明不直接影响 KSper/CatSper 的 NHEs 抑制剂，来研究 NHEs 在小鼠精子中对 KSper/CatSper 的功能。膜片钳记录结果表明，当细胞外 pH 值处于生理水平 7.4 时，DMA 应用会导致 KSper 抑制和膜电位去极化，而当管内溶液未 pH 缓冲时。相比之下，当管内溶液 pH 缓冲时，这些效应最小化，表明它们仅源于 NHEs 抑制引起的 pH 酸化。同样，DMA 处理降低了 CatSper 电流和细胞内 Ca，这一效应也依赖于管内溶液 pH 的缓冲能力。DMA 孵育后还观察到精子运动能力受损。这些结果表明，在生理条件下，NHEs 活性与 KSper/CatSper 的激活相关联。
