Zarintash R J, Cross N L
Department of Physiological Sciences, Oklahoma State University, Stillwater 74078-0353, USA.
Biol Reprod. 1996 Jul;55(1):19-24. doi: 10.1095/biolreprod55.1.19.
Human sperm become responsive to inducers of the acrosome reaction if they are washed free of seminal plasma and incubated in an appropriate medium. We tested the hypothesis that sperm must lose cholesterol during incubation in order to become responsive to the agonist, progesterone. Freshly ejaculated sperm contained 2.92 +/- 0.202 nmol unesterified cholesterol/10(7) sperm (mean +/- SEM, n = 18). When incubated for 24 h in vitro, sperm suspensions lost 29 +/- 6% of their free cholesterol (n = 23). Sperm lost cholesterol slightly faster than they became acrosomally responsive. Adding cholesterol to the medium prevented sperm from losing cholesterol and from becoming responsive. Varying the cholesterol content of the medium had similar effects on loss of sperm cholesterol (ED50 = 406 nM) and acrosomal responsiveness (ED50 = 388 nM). Incubating sperm with a 1:150 dilution of seminal plasma (containing 5.18 microM cholesterol) also prevented sperm from losing cholesterol and from becoming responsive. Incubating sperm 24 h in medium containing 0.5 mg/ml phosphatidylcholine increased the amount of cholesterol lost and the number of sperm that became responsive. Our results support a model in which sperm unesterified cholesterol (or a molecule in equilibrium with it) suppresses acrosomal responsiveness. Sperm must lose unesterified cholesterol to become responsive to progesterone.
如果将人类精子洗去精浆并在合适的培养基中孵育，它们就会对顶体反应诱导剂产生反应。我们检验了这样一个假说：精子在孵育过程中必须失去胆固醇才能对激动剂孕酮产生反应。刚射出的精子含有2.92±0.202 nmol游离胆固醇/10⁷个精子（平均值±标准误，n = 18）。在体外孵育24小时后，精子悬液失去了29±6%的游离胆固醇（n = 23）。精子失去胆固醇的速度略快于其产生顶体反应的速度。向培养基中添加胆固醇可阻止精子失去胆固醇并使其无法产生反应。改变培养基中的胆固醇含量对精子胆固醇的损失（半数有效浓度 = 406 nM）和顶体反应性（半数有效浓度 = 388 nM）有类似影响。用1:150稀释的精浆（含有5.18 μM胆固醇）孵育精子也可阻止精子失去胆固醇并使其无法产生反应。在含有0.5 mg/ml磷脂酰胆碱的培养基中孵育精子24小时会增加胆固醇的损失量以及产生反应的精子数量。我们的结果支持这样一个模型：精子游离胆固醇（或与其处于平衡状态的一种分子）会抑制顶体反应性。精子必须失去游离胆固醇才能对孕酮产生反应。
