Inhibition of G protein in human sperm and its influence on acrosome reaction and zona pellucida binding.

OBJECTIVE

To evaluate human sperm acrosomal status, zona pellucida (ZP)-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.

SETTING

Normal human sperm donors in an academic research environment.

INTERVENTION

Sperm were prepared with a wash and swim-up method and treated with a final concentration of 100 ng/mL pertussis toxin. Acrosomal status were determined using a Pisum sativum agglutinin-fluorescien-isothiocyanate method after exposure of sperm to 0.25, 0.5, 0.75, and 1.00 ZP/microL 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-reacted sperm, number of zona-bound sperm, and sperm motion parameters.

RESULTS

Spermatozoa treated with 100 ng/mL pertussis toxin, followed by ZP-mediated acrosome reaction induction, showed a significant decrease in the percentage of acrosome-reacted sperm compared with untreated controls. Motion characteristics of 3-hour capacitated sperm after treatment with either phosphate-buffered saline (PBS) or pertussis toxin were not different. Pertussis toxin-treated sperm populations bound significantly more sperm to the ZP after 4 hours incubation compared with the PBS-control groups: 137.1 +/- 8.0 compared with 96.3 +/- 7.0 (mean +/- SEM).

CONCLUSIONS

The data support the concept of the controlling mechanism and importance of G proteins during the ZP-mediated acrosome reaction. Intact acrosome correlate with and are needed to ensure tight zona binding.