Mechanisms of human sperm acrosome reaction

在本研究中，我们建立了同时测定人精子腺基嘌呤(ATP、ADP、AMP、腺苷、cAMP)的荧光标记-高效液相色谱(HPLC)体系。这一方法表明，包括cAMP在内的所有腺基嘌呤都不会因顶体反应而改变。咖啡因是最著名的促进人精子顶体反应的试剂，其作用机制被认为是通过抑制磷酸二酯酶(PDE)和随后细胞内cAMP的积累而出现的。本研究观察到咖啡因可显著增加人精子的活力、细胞内cAMP和顶体反应的诱导，而质膜通透性cAMP衍生物二丁酸cAMP和8BrcAMP促进精子活力，但不诱导顶体反应。我们发现乙酰胆碱(ACh)增强顶体反应而不增加运动和细胞内cAMP，然后这种作用被M受体拮抗剂阿托品竞争性地抑制。结果表明，细胞内cAMP可能在精子运动中起作用，而咖啡因对顶体反应的促进作用不是通过抑制PDE来实现的。顶体反应和运动分别发生在顶体和中段尾部。

In the present study, we established the fluorescent label-high performance liquid chromatography (HPLC) system for simultaneous measurement of human sperm adenyl purines (ATP,ADP,AMP,adenosine, cAMP). This method suggested that all the adenyl purines including cAMP did not change in consequence of the acrosome reaction. Caffeine is most well known agent to increase human sperm acrosome reaction and its mode of action is considered to be appeared through the inhibition of phosphodiesterase (PDE) and subsequent accumulation of intracellular cAMP.The present study observed that human sperm motility, intracellular cAMP and the induction of acrosome reaction were significantly increased in the presence of caffeine, whereas the plasma membrane permeable cAMP derivatives, dibutylic-cAMP and 8Br-cAMP accelerated sperm motility but not the induction of acrosome reaction. We found acetylcholine (ACh) enhanced the acrosome reaction without increasing the motility and intracellular cAMP.Then this action was suppressed competitively by atropine, a muscarinic antagonist. The present results indicate that intracellular cAMP may play a role in sperm motility, whereas acceleration of the acrosome reaction by means of caffeine is not appeared through the inhibition of PDE.The acrosome reaction and motility were the events occurred in the acrosome and midpiece-tail, respectively.