Leclerc P, Kopf G S
Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia 19104-6080, USA.
Biol Reprod. 1995 Jun;52(6):1227-33. doi: 10.1095/biolreprod52.6.1227.
It has been shown that the cAMP concentrations in capacitated mouse sperm can be increased in response to the egg's extracellular matrix, the zona pellucida (ZP), during the acrosome reaction. However, it is not known whether this cAMP elevation is caused by a stimulation of adenylyl cyclase (AC) activity or a decrease in cyclic nucleotide phosphodiesterase activity. In the present study using capacitated mouse spermatozoa, 20% and 30% of the total AC activity in the presence of Mg2+ and Mn2+, respectively, was measured in the sperm membrane fraction that contained the highest specific AC activity. As reported in other studies of sperm AC, Mn(2+)-supported AC activity was 15-30 times higher than Mg(2+)-supported AC activity. Interestingly, when the membrane fraction was solubilized with Lubrol-PX, an increase in specific and total Mg(2+)-supported AC activity was obtained while a decrease in both the specific and total Mn(2+)-supported AC activity was observed. In the absence of detergent, the ZP stimulates the membrane AC in a concentration-dependent manner, but this stimulation is observed only when the enzyme activity is measured in the presence of Mg2+. Forskolin also stimulates the Mg(2+)-but not the Mn(2+)-supported AC activity, and this effects is not additive to or synergistic with the ZP stimulation of the membrane AC. Results reported in this study suggest that ZP-mediated stimulation of membrane-associated AC may represent a mechanism by which the ZP affects sperm functions.
研究表明，在顶体反应过程中，获能小鼠精子中的环磷酸腺苷（cAMP）浓度会因卵子的细胞外基质——透明带（ZP）而升高。然而，尚不清楚这种cAMP升高是由腺苷酸环化酶（AC）活性的刺激还是环核苷酸磷酸二酯酶活性的降低引起的。在本研究中，使用获能的小鼠精子，在含有最高特异性AC活性的精子膜部分中，分别测定了在Mg2+和Mn2+存在下总AC活性的20%和30%。正如其他精子AC研究中所报道的，Mn(2+)支持的AC活性比Mg(2+)支持的AC活性高15 - 30倍。有趣的是，当用Lubrol - PX溶解膜部分时，特异性和总Mg(2+)支持的AC活性增加，而特异性和总Mn(2+)支持的AC活性均降低。在没有去污剂的情况下，ZP以浓度依赖的方式刺激膜AC，但这种刺激仅在Mg2+存在下测量酶活性时才观察到。福斯高林也刺激Mg(2+)支持的而非Mn(2+)支持的AC活性，并且这种作用与ZP对膜AC的刺激不是相加的或协同的。本研究报道的结果表明，ZP介导的对膜相关AC的刺激可能代表了ZP影响精子功能的一种机制。
