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Sperm membrane potential: hyperpolarization during capacitation regulates zona pellucida-dependent acrosomal
Y Zeng1, E N Clark, H M Florman
1Worcester Foundation for Biomedical Research, Shrewsbury, Massachusetts 01545, USA.
Developmental Biology
|October 1, 1995
Summary
Sperm membrane potential (VM) shifts during capacitation, becoming more negative. This hyperpolarization, linked to K+ permeability, is crucial for sperm to respond to zona pellucida stimuli.
Area of Science:
- Reproductive Biology
- Cell Physiology
- Spermatozoa Function
Background:
- Membrane potential (VM) is a critical factor in sperm function.
- Understanding VM changes during capacitation is essential for fertility research.
Purpose of the Study:
- To investigate and quantify VM in mouse and bovine sperm during capacitation.
- To elucidate the role of VM in sperm activation and response to stimuli.
Main Methods:
- Utilized fluorescent probes bis(1,3-diethylthiobarbituric acid)trimethine oxonol (DiSBAC2(3)) and 3,3'-dipropylthiodicarbocyanine iodide (DiSC3(5)) to measure VM.
- Calibrated VM measurements using selective sperm permeabilization with valinomycin or gramicidin D.
- Corrected fluorescent signals for mitochondrial potential contributions.
Main Results:
- Uncapacitated mouse and bovine sperm exhibited VM values of approximately -35 mV and -30 mV, respectively.
- Capacitated mouse and bovine sperm showed significantly hyperpolarized VM values ranging from -50 to -60 mV.
- Increased K+ permeability was identified as a contributing factor to membrane hyperpolarization.
Conclusions:
- Sperm capacitation involves significant membrane hyperpolarization.
- This hyperpolarization is essential for the development of signal transduction mechanisms activated by the zona pellucida.
- VM alterations regulate sperm activation, preventing premature acrosome reactions and enabling response to fertilization cues.