Purohit S B, Laloraya M, Kumar G P
School of Life Sciences, Devi Ahilya University, Indore, India.
Biochem Mol Biol Int. 1998 Jun;45(2):227-35. doi: 10.1080/15216549800202592.
Spin labeling studies of the lipophilic domains of human spermatozoa during capacitation and during acrosome reaction (AR) under the influence of selected AR-inducers were performed. Significantly enhanced rotational function of molecules was obvious during capacitation, with no significant changes in membrane packaging or the lateral diffusion of molecules. The AR inducers appeared to restrict the rotational freedom of molecules, dramatically enhancing the lateral diffusion and ordering coefficients. A significant decrease in superoxide anion generation was observed in the acrosome reacted groups when compared to the non-acrosome reacted groups. A high level of superoxide anion radical (O2.-) level maintained in capacitated spermatozoa would add to the Van der Waal's repulsive forces at the polar head of phospholipids, holding the membrane in strain where the molecular enjoy little freedom for lateral motion. A sudden drop in the levels of O2.- in spermatozoa upon addition of AR inducers could abruptly release the local hydrophobic repulsive strain within the membrane. This loss of hydration barrier explains the observed enhancement in lateral diffusion profiles of lipids and the packaging of molecules. It is reasonable to assume that these phenomena could be amplified further by interplay of Ca2+ by modifying the local charge aggregation. Thus, we would conclude that AR inducers release the oxyradical load in capacitated spermatozoa, which would modify the repulsive strain and hydration barrier forces in the lipophilic domains permitting vesiculation of the membranes. It appears that various acrosome reaction inducers act as effectors of grossly similar physical alterations in sperm membranes and that the resulting signal cascades proceed through intercalating biochemical sequences.
我们进行了自旋标记研究，以观察在特定顶体反应诱导剂的影响下，人精子在获能过程以及顶体反应（AR）期间亲脂结构域的情况。在获能过程中，分子的旋转功能显著增强，而膜包装或分子的侧向扩散没有明显变化。顶体反应诱导剂似乎限制了分子的旋转自由度，显著增强了侧向扩散和有序系数。与未发生顶体反应的组相比，发生顶体反应的组中超氧化物阴离子的产生显著减少。在获能精子中维持的高水平超氧阴离子自由基（O2.-）会增加磷脂极性头部的范德华排斥力，使膜处于张力状态，分子在其中几乎没有侧向运动的自由。加入顶体反应诱导剂后，精子中O2.-水平的突然下降可能会突然释放膜内局部的疏水排斥张力。这种水化屏障的丧失解释了所观察到的脂质侧向扩散分布和分子包装的增强。合理推测，通过改变局部电荷聚集，Ca2+的相互作用可能会进一步放大这些现象。因此，我们可以得出结论，顶体反应诱导剂释放了获能精子中的氧自由基负荷，这会改变亲脂结构域中的排斥张力和水化屏障力，从而允许膜泡化。看来，各种顶体反应诱导剂在精子膜中起着大体相似的物理改变效应器的作用，并且由此产生的信号级联通过插入生化序列进行。
