Brucker C, Lipford G B
I. Women's Hospital, Ludwig-Maximilians-University, Munich, Germany.
Hum Reprod Update. 1995 Jan;1(1):51-62. doi: 10.1093/humupd/1.1.51.
The acrosome reaction is a crucial step during gamete interaction in all species, including man. It allows spermatozoa to penetrate the zona pellucida and fuse with the oocyte membrane. Spermatozoa unable to undergo the acrosome reaction will not fertilize intact oocytes. This article concentrates on the characteristics and regulatory mechanisms of the acrosome reaction in human spermatozoa. During recent years, various entities found in the vicinity of the ovulated oocyte have been identified as stimulators of the acrosome reaction, of which zona protein is considered the prime physiological inducer in vivo. The steroid hormone progesterone has been shown to evoke critical responses in sperm cells leading to the acrosome reaction. Calcium has also been shown to play a central role during the acrosome reaction. Calcium flux is induced specifically by progesterone in capacitated and uncapacitated sperm cells, whereas only capacitated spermatozoa are able to subsequently complete the acrosome reaction. Progesterone as well as zona protein has been shown to evoke crucial responses within human spermatozoa, shedding light on the cascade of intracellular signalling events leading to the completion of the acrosome reaction. Furthermore, chemical agents which bring about the reaction in vitro, such as the ionophores ionomycin or A23187, have been used to shed light on its regulatory mechanisms. A number of molecules have been postulated to regulate the acrosome reaction in mammals, for example a galactosyl-transferase and a sperm protein tyrosine kinase. In addition, a novel protein, termed SAA-1, that was first detected on human spermatozoa is discussed with respect to its potential role as a regulatory protein closely involved in the initiation of the acrosome reaction.
顶体反应是包括人类在内的所有物种配子相互作用过程中的关键步骤。它使精子能够穿透透明带并与卵母细胞膜融合。无法发生顶体反应的精子将无法使完整的卵母细胞受精。本文着重探讨人类精子顶体反应的特征和调控机制。近年来，已确定排卵后的卵母细胞附近发现的各种物质是顶体反应的刺激物，其中透明带蛋白被认为是体内主要的生理诱导物。甾体激素孕酮已被证明能在精子细胞中引发关键反应，导致顶体反应。钙在顶体反应中也起着核心作用。孕酮能在获能和未获能的精子细胞中特异性诱导钙流，而只有获能的精子随后才能完成顶体反应。孕酮以及透明带蛋白已被证明能在人类精子中引发关键反应，从而揭示了导致顶体反应完成的细胞内信号事件级联。此外，能在体外引发该反应的化学试剂，如离子载体离子霉素或A23187，已被用于阐明其调控机制。已假定多种分子可调节哺乳动物的顶体反应，例如半乳糖基转移酶和一种精子蛋白酪氨酸激酶。此外，还讨论了一种首次在人类精子上检测到的新型蛋白质，即SAA - 1，关于它作为一种密切参与顶体反应起始的调控蛋白的潜在作用。
