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Sperm motility-inhibiting factor in rat epididymis
The American Journal of Physiology
|March 1, 1982
Summary
Spermatozoa remain immobile in rat cauda epididymidal fluid due to a protein. Removing proteins from this fluid allows sperm to become motile, suggesting a key factor for sperm quiescence in the male reproductive tract.
Area of Science:
- Reproductive Biology
- Sperm Physiology
- Male Reproductive Tract Biochemistry
Background:
- Spermatozoa in the cauda epididymidis are immotile in native fluid but become motile in saline.
- Epididymal fluid composition is crucial for maintaining sperm quiescence.
Purpose of the Study:
- To investigate the factors in epididymal fluid responsible for inhibiting sperm motility.
- To identify the origin of the motility-inhibiting substance.
Main Methods:
- Spermatozoa were collected from rat cauda epididymidis.
- Sperm motility was assessed after dilution in various fluids (cauda epididymidal fluid, NaCl, treated fluids).
- Proteins were removed from fluids via heat precipitation and enzymatic digestion.
Main Results:
- Cauda epididymidal fluid prevents sperm motility; 0.154 M NaCl promotes it.
- Protein removal from cauda fluid reduces its ability to inhibit sperm motility.
- Trypsin treatment of cauda fluid significantly increased sperm motility initiation.
- Proximal epididymal fluid and rete testis fluid showed reduced or no quiescence-inducing ability, respectively, though concentrated rete testis fluid inhibited motility.
Conclusions:
- A proteinaceous factor, likely of testicular origin, is responsible for inhibiting sperm motility initiation in the distal male reproductive tract.
- This factor plays a critical role in maintaining sperm quiescence during epididymal transit.