Zona pellucida-induced acrosome reaction in human sperm: dependency on activation of pertussis toxin-sensitive G(i) protein and extracellular calcium, and priming effect of progesterone and follicular fluid.

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Molecular human reproduction

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In these studies, we aimed to characterize the effects of the physiological, homologous agonists of the acrosome reaction, i.e. the zona pellucida (ZP) and progesterone/follicular fluid, on human sperm. The specific aims of our studies were: (i) to examine the dependency of the solubilized ZP-induced acrosome reaction on G(i) protein activation and presence of extracellular calcium; and (ii) to determine whether progesterone/follicular fluid exert a priming or synergist effect on the solubilized ZP-induced acrosome reaction. Highly motile sperm from fertile donors were exposed to the agonists in a microassay and the acrosomal status of live sperm was determined by indirect immunofluorescence using PSA-FITC/Hoechst double-staining. Pretreatment with pertussis-toxin (100 ng/ml) and EGTA (2.5 mmol/l) significantly inhibited the ZP-induced acrosome reaction without affecting the spontaneous rate of exocytosis. Progesterone (1.25 microg/ml) and human follicular fluid (10%) exerted a priming, time-dependent effect on the ZP-induced acrosome reaction. These studies demonstrated that: (i) acrosomal exocytosis of capacitated human sperm triggered by the homologous ZP is dependent on the activation of G(i) proteins (pertussis toxin-sensitive) and the presence of extracellular calcium; and (ii) progesterone and follicular fluid exert a priming effect on the ZP-induced acrosome reaction.


Acrosome Reaction, Analysis of Variance, Calcium, Female, Follicular Fluid, GTP-Binding Protein alpha Subunits, Gi-Go, Humans, Male, Progesterone, Spermatozoa, Zona Pellucida

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Molecular human reproduction (2002) 8:8, pp. 722-727.

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