Modulation of human sperm function by peritoneal fluid

OBJECTIVE: To examine the effect of peritoneal fluid on various parameters of sperm function in vitro. DESIGN: Prospective study. SETTING: Basic research laboratory. PATIENT(S): Semen samples were obtained from normozoospermic volunteers (n = 43). Peritoneal fluids were aspirated laparoscopically from women with unexplained infertility (n = 14). Follicular fluid and oocytes were collected from patients undergoing IVF-ET. INTERVENTION(S): Sperm incubated under capacitating conditions were exposed to peritoneal fluid, and functional variables were evaluated in vitro. MAIN OUTCOME MEASURE(S): Sperm viability and motility, follicular fluid and calcium ionophore-induced acrosome reactions, protein tyrosine phosphorylation, expression of D-mannose binding sites, and ability of sperm to interact with zona pellucida. RESULT(S): Exposure of sperm to peritoneal fluid for up to 6 hours did not affect sperm viability or motility. Unlike follicular fluid, peritoneal fluid did not induce the acrosome reaction. Moreover, incubation of sperm with > or =20% v/v peritoneal fluid for 1 hour prevented the follicular fluid and the ionophore-induced acrosome reaction. Although treatment with peritoneal fluid allowed protein tyrosine phosphorylation during capacitation, it resulted in a significant decrease in the expression of D-mannose binding sites and sperm-zona pellucida binding. CONCLUSION(S): Peritoneal fluid maintains sperm survival and decreases sperm ability to respond to inducers of the acrosome reaction and bind to the zona pellucida in vitro, indicating that this fluid might modulate sperm function in vivo.