INHIBITION OF C-PROTEIN IN HUMAN SPERM AND ITS INFLUENCE ON ACROSOME REACTION AND ZONA-PELLUCIDA BINDING

Objective: To evaluate human sperm acrosomal status, zona pellucida (Z P)-binding capacity, and sperm motion characteristics after treatment with pertussis toxin followed by exposure to increasing concentrations of solubilized human ZP. Design: Prospective analytical study. Settin g: Normal human sperm donors in an academic research environment. Inte rvention: Sperm were prepared with a wash and swim-up method and treat ed with a final concentration of 100 ng/mL pertussis toxin. Acrosomal status were determined using a Pisum sativum agglutinin-fluorescien-is othiocyanate method after exposure of sperm to 0.25, 0.5, 0.75, and 1. 00 ZP/mu L solutions of human ZP. Zona binding potential was recorded using intact zona-binding assays. Motion characteristics were recorded with a semen analyzer. Main Outcome Measure: Percentage acrosome-reac ted sperm, number of zona-bound sperm, and sperm motion parameters. Re sults: Spermatozoa treated with 100 ng/mL pertussis toxin, followed by ZP-mediated acrosome reaction induction, showed a significant decreas e in the percentage of acrosome-reacted sperm compared with untreated controls. Motion characteristics of S-hour capacitated sperm after tre atment with either phosphate-buffered saline (PBS) or pertussis toxin were not different. Pertussis toxin-treated sperm populations bound si gnificantly more sperm to the ZP after 4 hours incubation compared wit h the PBS-control groups: 137.1 +/- 8.0 compared with 96.3 +/- 7.0 (me an +/- SEM). Conclusions: The data support the concept of the controll ing mechanism and importance of G proteins during the ZP-mediated acro some reaction. Intact acrosomes correlate with and are needed to ensur e tight zona binding.