Bovine sperm hyperactivation is promoted by alkaline-stimulated Ca2+ influx
Bovine sperm hyperactivation is promoted by alkaline-stimulated Ca2+ influx
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DOI：
10.1095/biolreprod.106.055038
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发表时间：
2007-04-01
影响因子：
3.6
通讯作者：
Suarez, Susan S.
中科院分区：
文献类型：
--
作者：
Marquez, Becky;Suarez, Susan S.
精子活力过度活跃的特点是鞭毛弯曲幅度高和不对称跳动，通过计算机辅助精子活力分析可检测到曲线速度增加和头部横向运动。它是受精过程中精子穿透卵母细胞透明带所必需的，并且由鞭毛 Ca2+ 的增加诱导。我们的目标是确定 pH 值是否在促进过度活跃的运动的 Ca 信号传导中发挥作用。细胞渗透性弱碱 NH4Cl 增加了牛精子侧向头部运动的曲线速度和幅度，表明过度激活。装载 BCECF-AM 或 Fluo3-AM 的精子的荧光记录显示，NH4Cl 分别引起细胞内 pH 值和 Ca2+ 升高，且 pH 值升高的速度比 Ca2+ 更快。单细胞图像分析显示，鞭毛中的 Ca2+ 水平因 NH4Cl 的反应而增加。当在用 NH4Cl 处理之前用 BAPTA（1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸）降低细胞外 Ca2+ 时，细胞内 pH 值升高，但 Ca2+ 升高和过度激活减弱。这表明细胞内 pH 值的升高先于 Ca2+ 的流入。 Ca2+ 通道阻滞剂 Ni2+ 也减少了 NH4Cl 对过度激活的刺激，表明 Ca2+ 进入是过度激活最大程度表达所必需的。 Call 离子载体产生的 Call 增加是 NH4Cl 产生的 3 倍；然而，它产生的过度激活反应较弱。这些结果表明，pH 值升高主要通过刺激 Ca2+ 流入增加细胞内 Ca2+ 并促进过度激活，但也通过其他机制。
Sperm hyperactivated motility is characterized by high flagellar bend amplitude and asymmetrical beating, which are detected by computer-assisted sperm motility analysis as increased curvilinear velocity and lateral head movement. It is required for sperm penetration of the oocyte zona pellucida during fertilization and is induced by an increase in flagellar Ca2+. Our objective was to determine whether pH plays a role in promoting Ca signaling of hyperactivated motility. The cell-permeant weak base NH4Cl increased curvilinear velocity and amplitude of lateral head movement of bovine sperm, indicative of hyperactivation. Fluorometric recordings of sperm loaded with BCECF-AM or fluo3-AM, revealed that NH4Cl evoked elevations of intracellular pH and Ca2+, respectively, with the rise in pH occurring more rapidly than that of Ca2+. Single-cell image analysis showed increased Ca2+ levels in the flagellum in response to NH4Cl. When extracellular Ca2+ was lowered with BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) prior to treatment with NH4CI, intracellular pH was increased, but elevation of Ca2+ and hyperactivation were diminished. This suggests that the rise in intracellular pH precedes an influx of Ca2+. The Ca2+ channel blocker Ni2+ also diminished NH4Cl stimulation of hyperactivation, demonstrating that Ca2+ entry is required for maximal expression of hyperactivation. Call ionophore produced an increase in Call that was 3-fold greater than that produced by NH4Cl; however, it produced a weaker hyperactivation response. These results indicate that a rise in pH increases intracellular Ca2+ and promotes hyperactivation primarily by stimulating Ca2+ influx, but also by other mechanisms.