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REVERSIBLE INHIBITION OF SPERM-EGG FUSION IN THE HAMSTER BY LOW PH
Ryuzo Yanagimachi1, Lawrence H Miyashiro1, Hiroko Yanagimachi1
1Department of Anatomy and Reproductive Biology, University of Hawaii School of Medicine, Honolulu, Hawaii 96822, U.S.A.
Development, Growth & Differentiation
|June 7, 2023
Summary
Sperm-egg fusion requires a specific pH environment. Maintaining a pH above 7.1 is crucial for successful fertilization, as lower pH levels inhibit sperm fusion with the egg.
Area of Science:
- Reproductive Biology
- Cell Biology
- Biochemistry
Background:
- Sperm-egg fusion is a critical step in fertilization.
- The influence of environmental factors like pH on this process is not fully understood.
Purpose of the Study:
- To investigate the impact of varying pH levels on sperm-egg fusion in vitro.
- To determine the threshold pH for successful sperm-egg fusion.
Main Methods:
- Hamster eggs were denuded of cumulus oophorus and zona pellucida.
- Acrosome-reacted spermatozoa were used to inseminate eggs in media buffered to different pH values (using phosphate, Hepes, and Bes buffers).
- Sperm penetration and fusion were assessed microscopically.
Main Results:
- 100% egg penetration occurred at pH > 7.1.
- Penetration rates decreased significantly below pH 7.0, reaching 0% at pH 6.1.
- At low pH (6.0-6.1), sperm could bind to the egg but fusion was blocked.
- The fusion block at low pH was reversible upon return to alkaline conditions.
Conclusions:
- Optimal pH for hamster sperm-egg fusion is above 7.1.
- Low pH reversibly inhibits sperm-egg fusion, specifically the fusion step after initial binding.
- These findings highlight the importance of precise pH control in assisted reproductive technologies.
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