De Jonge C J, Han H L, Lawrie H, Mack S R, Zaneveld L J
Department of Obstetrics and Gynecology, Rush University, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612-3864.
J Exp Zool. 1991 Apr;258(1):113-25. doi: 10.1002/jez.1402580113.
The acrosome reaction of spermatozoa appears to be analogous to various somatic cell exocytotic events which involve cascade reactions, i.e., transmission of an external signal across the cell membrane resulting in activation of an "amplifier" enzyme and the generation of a second messenger. Using a synchronous acrosome reaction system (De Jonge et al., J. Androl., 10:232-239, '89a), it was found that analogues of the second-messenger cAMP, dibutyryl cAMP (dbcAMP) and 8-bromo cAMP, stimulated the acrosome reaction of capacitated spermatozoa. Additionally, treatment of spermatozoa with either xanthine or non-xanthine phosphodiesterase inhibitors induced a significant (P less than 0.05) increase in the percent acrosome reaction after a period of capacitation in comparison to untreated controls. These results indicate that analogues of cAMP or inhibitors which prevent cAMP hydrolysis can induce the human sperm acrosome reaction. Subsequent experiments were conducted to test whether the amplifier enzyme in the cascade reaction, adenylate cyclase, has a role in the acrosome reaction. Forskolin, an adenylate cyclase stimulator, caused a significant (P less than 0.01) increase in the percent acrosome reaction in comparison to controls. Modulators of adenylate cyclase--adenosine, 2'-0-methyladenosine, and 2',3'-dideoxyadenosine--significantly (P less than 0.01) inhibited the forskolin-induced acrosome reaction. dbcAMP was able to overcome the inhibition by adenosine. Two inhibitors of protein kinase A, the Walsh inhibitor and H-8, caused a significant (P less than 0.01) inhibition of the dbcAMP-induced acrosome reaction. Finally, in the absence of extracellular calcium, dbcAMP induced a significant (P less than 0.01) increase in the acrosome reaction in contrast to A23187. These results suggest that: 1) a molecular mechanism for the human sperm acrosome reaction involves the cAMP second-messenger system; i.e., activation of adenylate cyclase, the amplifier enzyme that produces cAMP, production of cAMP as a second messenger, and activation of cAMP-dependent kinase A; and that 2) activation of adenylate cyclase occurs after calcium influx.
精子的顶体反应似乎类似于各种体细胞的胞吐事件，这些事件涉及级联反应，即外部信号穿过细胞膜，导致“放大”酶的激活和第二信使的产生。使用同步顶体反应系统（De Jonge等人，《雄性学杂志》，10:232 - 239，'89a），发现第二信使cAMP的类似物，二丁酰cAMP（dbcAMP）和8 - 溴cAMP，刺激了获能精子的顶体反应。此外，用黄嘌呤或非黄嘌呤磷酸二酯酶抑制剂处理精子，与未处理的对照相比，在获能一段时间后，顶体反应百分比显著（P小于0.05）增加。这些结果表明，cAMP的类似物或防止cAMP水解的抑制剂可以诱导人类精子顶体反应。随后进行了实验，以测试级联反应中的放大酶腺苷酸环化酶是否在顶体反应中起作用。福斯可林，一种腺苷酸环化酶刺激剂，与对照相比，导致顶体反应百分比显著（P小于0.01）增加。腺苷酸环化酶的调节剂——腺苷、2'-O-甲基腺苷和2'，3'-二脱氧腺苷——显著（P小于0.01）抑制了福斯可林诱导的顶体反应。dbcAMP能够克服腺苷的抑制作用。两种蛋白激酶A抑制剂，沃尔什抑制剂和H - 8，导致dbcAMP诱导的顶体反应显著（P小于0.01）抑制。最后，在没有细胞外钙的情况下，与A23187相比，dbcAMP诱导顶体反应显著（P小于0.01）增加。这些结果表明：1）人类精子顶体反应的分子机制涉及cAMP第二信使系统；即腺苷酸环化酶的激活，产生cAMP的放大酶，作为第二信使的cAMP的产生以及cAMP依赖性蛋白激酶A的激活；并且2）腺苷酸环化酶的激活发生在钙内流之后。
