G-protein regulation of the solubilized human zona pellucida-mediated acrosome reaction and zona pellucida binding.
OBJECTIVE
The study aimed to evaluate the (i) regulatory role of Gi-like protein during the acrosome reaction (AR) of normal sperm donors and (ii) the role of intact acrosomes during sperm-zona binding.


METHODS
The acrosomal exocytosis of spermatozoa incubated with solubilized zona pellucida (ZP) at a final concentration of 1 ZP/microliter was compared with 10 microM calcium ionophore A23187 and 30% (v/v) pooled human follicular fluid (HFF). Spermatozoa were incubated with 1, 10, and 100 ng/ml pertussis toxin (PT) during capacitation to functionally inactivate the Gi-like protein. The sperm-zona binding potential of 100 ng/ml PT-treated spermatozoa followed, by exposure to 1 ZP/microliter, revealed significantly higher zona-bound spermatozoa compared to controls treated with 1 ZP/microliter only.


RESULTS
PT treatment of spermatozoa did not affect sperm motility, however, inhibited the percentage AR induced by solubilized ZP. In contrast, the A23187- and HFF-induced ARs were not sensitive to PT treatment. PT inhibition of the ZP-induced AR occurred in a concentration-dependent manner, with maximal effects observed at 100 ng/ml PT.


CONCLUSIONS
In conclusion, it seems that PT-sensitive Gi-like protein in human spermatozoa plays an important regulatory role in the AR induced by the human ZP, and this underlines the importance of intact acrosomes during sperm-zona binding.
Bastiaan
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H
Department of Obstetrics & Gynaecology, University of Stellenbosch, Tygerberg Hospital, South Africa.
Franken
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Wranz
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P
D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D005089:Exocytosis; D005260:Female; D015571:Follicular Fluid / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D006801:Humans; D008297:Male; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D037342:Pertussis Toxin; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D015044:Zona Pellucida / Q000502:physiology*
D010566:Virulence Factors, Bordetella; D000001:Calcimycin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins