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Progesterone induces hyperpolarization after a transient depolarization phase in human spermatozoa
C Patrat1, C Serres, P Jouannet
1GREFH-Laboratoire d'Histologie-Embryologie et Biologie de la Reproduction, Hôpital Cochin, Faculté de Médecine Cochin-Port-Royal, Université Paris V, 75014 Paris, France. catherine.patrat@cch.ap-hop-paris.fr
Biology of Reproduction
|May 22, 2002
Summary
Progesterone (P4) alters human sperm membrane potential, causing depolarization and repolarization. This influences sperm subpopulations, potentially enhancing their ability to undergo the acrosome reaction (AR) when interacting with the zona pellucida.
Area of Science:
- Human reproductive biology
- Sperm physiology
- Membrane biophysics
Background:
- Progesterone (P4) is crucial for initiating the human sperm acrosome reaction (AR).
- P4 triggers membrane depolarization and ion fluxes necessary for AR.
- Understanding P4's precise effects on sperm membrane potential is key to reproductive research.
Purpose of the Study:
- To quantify and analyze progesterone-induced changes in capacitated human sperm membrane potential.
- To investigate the role of ion fluxes in P4-mediated membrane potential modifications.
- To explore the heterogeneity of these responses within sperm populations.
Main Methods:
- Spectrofluorimetry using the potentiometric dye DiSC3(5) to measure membrane potential.
- Flow cytometry to analyze membrane potential heterogeneity in sperm subpopulations.
- Application of 10 microM P4 to capacitated human spermatozoa.
Main Results:
- Mean resting sperm membrane potential was -58 ± 2 mV.
- 10 microM P4 induced an average depolarization of +15 mV, partly via chloride efflux.
- A subsequent repolarization occurred in two-thirds of samples, reaching a hyperpolarized state.
- Flow cytometry revealed heterogeneous responses, with only 3-40% of cells showing depolarization-hyperpolarization events.
Conclusions:
- Progesterone induces complex membrane potential changes in human sperm, including depolarization and subsequent hyperpolarization in specific subpopulations.
- These P4-induced membrane potential shifts may prime a sperm subpopulation for the acrosome reaction.
- Hyperpolarized sperm cells might be more receptive to zona pellucida-induced calcium influx via T-type calcium channels, enhancing fertilization potential.