Purohit S B, Laloraya M, Kumar G P
School of Life Sciences, Devi Ahilya University, Vigyan Bhavan, Khandwa Road, Indore 452001, M.P., India.
Asian J Androl. 1999 Sep;1(3):95-107.
Capacitation and acrosome reaction are important prerequisites of the fertilization process. Capacitation is a highly complex phenomenon occurring in the female genital tract, rendering the spermatozoa capable of binding and fusion with the oocyte. During capacitation various biochemical and biophysical changes occur in the spermatozoa and the spermatozoal membranes. Ions and ion channels also play important roles in governing the process of capacitation by changing the fluxes of different ions which in turn controls various characteristics of capacitated spermatozoa. Along with the mobilization of ions the generation of free radicals and efflux of cholesterol also plays an important role in the capacitation state of the spermatozoa. The generation of free radical and efflux of cholesterol change the mechanodynamic properties of the membrane by oxidation of the polyunsaturated lipids and by generating the cholesterol free patches. The process of capacitation renders the spermatozoa responsive to the inducers of the acrosome reaction. The glycoprotein zona pellucida 3 (ZP3) of the egg coat zona pellucida is the potent physiological stimulator of the acrosome reaction; progesterone, a major component of the follicular fluid, is also an inducer of the acrosome reaction. The inducers of the acrosome reaction cause the activation of the various ion-channels leading to high influxes of calcium, sodium and bicarbonate. The efflux of cholesterol during the process of capacitation alters the permeability of the membrane to the ions and generate areas which are prone to fusion and vesiculation process during the acrosome reaction. This review focuses mainly on effects of the ion and ion-channels, free radicals, and membrane fluidity changes during the process of capacitation and acrosome reaction.
获能和顶体反应是受精过程的重要前提条件。获能是发生在雌性生殖道中的一种高度复杂的现象，使精子能够与卵母细胞结合并融合。在获能过程中，精子及精子膜会发生各种生化和生物物理变化。离子和离子通道也通过改变不同离子的通量来控制获能过程，进而控制获能精子的各种特性，在调控获能过程中发挥重要作用。除了离子的动员，自由基的产生和胆固醇的外流在精子的获能状态中也起着重要作用。自由基的产生和胆固醇的外流通过多不饱和脂质的氧化和产生无胆固醇斑块来改变膜的机械动力学特性。获能过程使精子对顶体反应的诱导剂产生反应。卵透明带的糖蛋白透明带3（ZP3）是顶体反应的有效生理刺激物；卵泡液的主要成分孕酮也是顶体反应的诱导剂。顶体反应的诱导剂会导致各种离子通道的激活，从而使钙、钠和碳酸氢根大量内流。获能过程中胆固醇的外流改变了膜对离子的通透性，并产生了在顶体反应过程中易于融合和形成囊泡的区域。本综述主要关注获能和顶体反应过程中离子和离子通道、自由基以及膜流动性变化的影响。
