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Boar sperm plasma membrane Ca(2+)-selective channels in planar lipid bilayers
1Department of Physiology, School of Medicine, Southern Illinois University, Carbondale 62901, USA.
The American Journal of Physiology
|May 1, 1995
Summary
Calcium channels in boar sperm are activated by dihydropyridines and blocked by antagonists, suggesting their role in the acrosome reaction crucial for fertilization.
Area of Science:
- Reproductive Biology
- Ion Channel Physiology
- Molecular Pharmacology
Background:
- Calcium influx via Ca2+ channels triggers the sperm acrosome reaction, essential for fertilization.
- L-type Ca2+ channel antagonists inhibit intracellular Ca2+ increase and acrosomal exocytosis in mammalian sperm.
Purpose of the Study:
- To characterize Ca2+ channels in boar sperm plasma membranes using electrophysiological methods.
- To investigate the role of these channels in regulating intracellular Ca2+ levels preceding the acrosome reaction.
Main Methods:
- Planar bilayer recordings of partially purified boar sperm plasma membranes.
- Application of dihydropyridine agonist (+/-)BAY K 8644 and antagonist nitrendipine.
- Analysis of single-channel events and dose-dependent effects on channel activity.
Main Results:
- Identified Ca2+ channels permeable to Ba2+ in boar sperm membranes.
- Channels were activated by (+/-)BAY K 8644 and inhibited by nitrendipine.
- Activation and inhibition kinetics were dose-dependent, with specific affinities for enantiomers.
Conclusions:
- Boar sperm Ca2+ channels are modulated by dihydropyridines, similar to L-type channels in other tissues.
- These channels do not require depolarization and do not inactivate, suggesting a unique regulatory mechanism.
- The findings support the involvement of these Ca2+ channels in elevating intracellular Ca2+ for the acrosome reaction.