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Calcium dependence of human sperm fertilizing ability
D Mortimer1, M J Chorney, E F Curtis
1Department of Ob/Gyn, University of Calgary, Alberta, Canada.
The Journal of Experimental Zoology
|May 1, 1988
Summary
Strontium ions (Sr2+) can replace calcium ions (Ca2+) for human sperm capacitation and acrosome reactions. However, Ca2+ is crucial for sperm-zona and sperm-oolemma interactions, impacting fertilization ability.
Area of Science:
- Reproductive Biology
- Sperm Physiology
- In Vitro Fertilization
Background:
- Calcium ions (Ca2+) are essential for human sperm function, including fertilization.
- The specific roles of Ca2+ in different stages of sperm-egg interaction require further elucidation.
Purpose of the Study:
- To investigate the dependency of human sperm fertilizing ability on Ca2+.
- To determine if strontium ions (Sr2+) can substitute for Ca2+ in sperm capacitation and acrosome reactions.
- To examine the role of Ca2+ in sperm-zona pellucida and sperm-oolemma interactions.
Main Methods:
- Human sperm were incubated in modified Tyrode's medium with either CaCl2 (CA medium) or SrCl2 (SREG-medium).
- Acrosome reactions were assessed using fluorescent lectin labelling and triple stain.
- Sperm-zona binding and hamster egg penetration tests (HEPT) were performed.
Main Results:
- Sr2+ fully substituted for Ca2+ in supporting sperm capacitation and acrosome reactions.
- Significantly more sperm bound to zona pellucidae in CA medium compared to SREG-medium.
- Fertilization rates in HEPT were substantially higher in CA medium than in SREG-medium, despite similar capacitation and acrosome reaction kinetics.
Conclusions:
- While Sr2+ can support human sperm capacitation and acrosome reactions, Ca2+ is indispensable for sperm-zona and sperm-oolemma interactions.
- The fertilizing ability of human sperm is not solely dependent on the kinetics of capacitation or acrosome reactions.
- Ca2+-specific mechanisms are involved in the later stages of human sperm-egg fusion.