Department of Medical Biology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, 930-0194, Japan.
Reproduction. 2011 Feb;141(2):163-71. doi: 10.1530/REP-10-0201. Epub 2010 Nov 11.
The developing acrosome in spermatids contains pituitary adenylate cyclase-activating polypeptide (PACAP). However, the role of the acrosomal PACAP remains unclear because it has not been detected in mature spermatids and sperm. We reinvestigated whether the sperm acrosome contains PACAP. An antiserum produced against PACAP reacted to the anterior acrosome in epididymal sperm fixed under mild conditions, suggesting that PACAP acts on oocytes and/or cumulus cells at the site of fertilization. Immunolabeling and RT-PCR demonstrated the presence of PACAP type I receptor, a PACAP-specific receptor, in postovulatory cumulus cells. To investigate the role of PACAP in fertilization, we pretreated cumulus-oocyte complexes with the polypeptide. At a low concentration of sperm, the fertilization rate was significantly enhanced by PACAP in a dose-dependent manner. Sperm penetration through the oocyte investment, cumulus layer, and zona pellucida was also enhanced by PACAP. The enhancement was probably due to an enhancement in sperm motility and the zona-induced acrosome reaction, which were stimulated by a cumulus cell-releasing factor. Indeed, PACAP treatment increased the secretion of progesterone from the cumulus-oocyte complexes. These results strongly suggest that in response to PACAP, cumulus cells release a soluble factor that probably stimulates sperm motility and the acrosome reaction, thereby promoting fertilization.
精子顶体中含有垂体腺苷酸环化酶激活肽（PACAP）。然而，由于成熟精子和精子中未检测到顶体 PACAP，其作用尚不清楚。我们重新研究了精子顶体是否含有 PACAP。针对 PACAP 产生的抗血清与在温和条件下固定的附睾精子的前顶体反应，提示 PACAP 在受精部位作用于卵母细胞和/或卵丘细胞。免疫标记和 RT-PCR 表明，排卵后卵丘细胞中存在 PACAP 型 I 受体，即 PACAP 特异性受体。为了研究 PACAP 在受精中的作用，我们用该多肽预处理卵丘-卵母细胞复合物。在低浓度精子的情况下，PACAP 以剂量依赖的方式显著增强了受精率。PACAP 还增强了精子穿透卵母细胞包被、卵丘层和透明带。这种增强可能是由于精子运动和由卵丘细胞释放因子刺激的透明带诱导的顶体反应增强所致。事实上，PACAP 处理增加了卵丘-卵母细胞复合物中孕酮的分泌。这些结果强烈表明，对 PACAP 的反应，卵丘细胞释放一种可溶性因子，可能刺激精子运动和顶体反应，从而促进受精。
