Cross N L
Department of Physiological Sciences, Oklahoma State University, Stillwater 74078-0353, USA.
Mol Reprod Dev. 1996 Oct;45(2):212-7. doi: 10.1002/(SICI)1098-2795(199610)45:2<212::AID-MRD14>3.0.CO;2-2.
Human sperm become responsive to inducers of the acrosome reaction when they are washed free of seminal plasma and incubated in an appropriate medium. Previous work has shown that cholesterol-enriched medium prevents sperm from becoming responsive to the inducer, progesterone. Sperm that were incubated 24 hr in cholesterol-enriched medium and then treated with progesterone showed no evidence of membrane fusion, indicating that cholesterol acts at a stage before the earliest morphological change. Inhibition of acrosomal responsiveness by cholesterol was reversible. Among other sterols reported in mammalian sperm, desmosterol and cholesterol sulfate also inhibited sperm from becoming responsive, but cholesterol palmitate did not. Our results support a model in which sperm unesterified cholesterol, or a molecule in equilibrium with it, suppresses acrosomal responsiveness. Cholesterol-enriched medium also prevented sperm from becoming responsive to the calcium/proton exchanging ionophore, ionomycin, suggesting that cholesterol's effect may be, at least in part, at a point in the signal transduction pathway subsequent to the rise in intracellular-free calcium.
当人类精子被洗去精浆并在合适的培养基中孵育时，它们会对顶体反应诱导剂产生反应。先前的研究表明，富含胆固醇的培养基会阻止精子对诱导剂孕酮产生反应。在富含胆固醇的培养基中孵育24小时后再用孕酮处理的精子，没有显示出膜融合的迹象，这表明胆固醇在最早的形态变化之前的阶段起作用。胆固醇对顶体反应性的抑制是可逆的。在哺乳动物精子中报道的其他固醇中，去氢胆固醇和硫酸胆固醇也会抑制精子产生反应，但棕榈酸胆固醇不会。我们的结果支持这样一个模型，即精子中的未酯化胆固醇或与其处于平衡状态的分子会抑制顶体反应性。富含胆固醇的培养基也会阻止精子对钙/质子交换离子载体离子霉素产生反应，这表明胆固醇的作用可能至少部分是在细胞内游离钙升高后的信号转导途径中的某个点上。
