Mechanisms of human sperm acrosome reaction

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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.