Bielfeld P, Anderson R A, Mack S R, De Jonge C J, Zaneveld L J
Rush University, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612.
Fertil Steril. 1994 Dec;62(6):1255-61. doi: 10.1016/s0015-0282(16)57195-7.
To determine if the acrosome reaction of human spermatozoa can occur without prior incubation to induce capacitation or in calcium-free medium.
Noncapacitated (washed ejaculated) or capacitated (incubated for 3 hours in the presence of albumin) human spermatozoa were treated with either solubilized zonae pellucidae (ZP); a calcium ionophore (A23187); or activators of protein kinases A, G, and C, and the acrosomal status was monitored by the double stain technique. During agonist treatment, the capacitated spermatozoa were in medium either with or without calcium ions (Ca2+). The noncapacitated spermatozoa were always in Ca(2+)-containing medium. Sperm motility was monitored throughout the experiments.
Solubilized ZP and kinase activators induced acrosomal exocytosis of capacitated spermatozoa (both in Ca(2+)-containing and Ca(2+)-free medium) and of noncapacitated spermatozoa. The lack of added Ca2+ or capacitation reduced the percentage of spermatozoa that reacted in response to solubilized ZP but not to the kinase activators. Ionophore A23187 stimulated acrosomal loss from noncapacitated spermatozoa to the same extent as capacitated spermatozoa in Ca(2+)-containing medium but had no effect on capacitated spermatozoa in Ca(2+)-free medium.
Human spermatozoa do not require incubation under capacitating conditions or the presence of extracellular Ca2+ before they can undergo the acrosome reaction in response to certain agonists. Therefore, Ca2+ influx and/or preincubation to induce capacitation are not absolute requirements for the in vitro agonist-induced acrosome reaction. However, these conditions can optimize the acrosome reaction response to zona proteins. The intracellular mechanisms leading to the acrosome reaction appear to be functional in noncapacitated spermatozoa but membrane changes probably are required before certain extracellular ligands such as zona proteins can exert their maximal effect.
确定人类精子的顶体反应是否能在未经诱导获能的预孵育情况下或在无钙培养基中发生。
未获能（洗涤后的射出精子）或获能（在白蛋白存在下孵育3小时）的人类精子用溶解的透明带（ZP）、钙离子载体（A23187）或蛋白激酶A、G和C的激活剂处理，并用双重染色技术监测顶体状态。在激动剂处理期间，获能精子处于含或不含钙离子（Ca2+）的培养基中。未获能精子始终处于含钙（Ca2+）的培养基中。在整个实验过程中监测精子活力。
溶解的ZP和激酶激活剂诱导获能精子（在含钙和无钙培养基中）以及未获能精子发生顶体外排。缺乏添加的Ca2+或获能降低了对溶解的ZP作出反应的精子百分比，但对激酶激活剂无此影响。离子载体A23187在含钙培养基中刺激未获能精子顶体丢失的程度与获能精子相同，但对无钙培养基中的获能精子无影响。
人类精子在对某些激动剂发生顶体反应之前，不需要在获能条件下孵育或存在细胞外Ca2+。因此，Ca2+内流和/或预孵育以诱导获能不是体外激动剂诱导顶体反应的绝对必要条件。然而，这些条件可以优化对透明带蛋白的顶体反应。导致顶体反应的细胞内机制在未获能精子中似乎是起作用的，但在某些细胞外配体如透明带蛋白发挥最大作用之前，可能需要膜的变化。
