PACAP-mediated sperm-cumulus cell interaction promotes fertilization.
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.
Department of Medical Biology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, 930-0194, Japan.
Ichiro
I
Tanii
Tadashi
T
Aradate
Kouhei
K
Matsuda
Akira
A
Komiya
Hideki
H
Fuse
D000177:Acrosome / Q000378:metabolism; D000818:Animals; D017077:Culture Media, Conditioned / Q000494:pharmacology; D054885:Cumulus Cells / Q000378:metabolism*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005307:Fertilization in Vitro; D005455:Fluorescent Antibody Technique; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009865:Oocytes / Q000502:physiology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000502:physiology*; D011374:Progesterone / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013081:Sperm Motility; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*
C495402:Adcyap1 protein, mouse; D017077:Culture Media, Conditioned; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011453:Prostaglandins; D012333:RNA, Messenger; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011374:Progesterone