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Sperm, inositol trisphosphate, and thimerosal-induced intracellular Ca2+ elevations in rabbit eggs
1Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst 01003.
Developmental Biology
|September 1, 1993
Summary
Fertilized rabbit eggs show repeated calcium (Ca2+) rises, crucial for reproduction. Inositol 1,4,5 trisphosphate (InsP3) and thimerosal trigger these Ca2+ releases, likely from a shared intracellular store.
Area of Science:
- Reproductive Biology
- Cellular Physiology
- Biochemistry
Background:
- Fertilization triggers complex intracellular events in mammalian eggs.
- Calcium (Ca2+) signaling plays a pivotal role in regulating fertilization and early embryonic development.
- Understanding the mechanisms of Ca2+ release is key to comprehending reproductive success.
Purpose of the Study:
- To investigate fertilization-induced calcium (Ca2+) changes in rabbit eggs.
- To explore the role of inositol 1,4,5 trisphosphate (InsP3) and thimerosal in intracellular Ca2+ release.
- To identify the signaling pathways involved in Ca2+ dynamics during rabbit egg fertilization.
Main Methods:
- Utilized fura-2 dextran, a fluorescent Ca2+ indicator, to monitor Ca2+ levels in vivo fertilized rabbit eggs.
- Administered inositol 1,4,5 trisphosphate (InsP3) and its analogue InsP3S3 via microinjection.
- Applied thimerosal and heparin (InsP3 receptor antagonist) to assess their effects on Ca2+ release.
- Performed experiments in Ca(2+)-free medium to analyze successive agonist applications.
Main Results:
- Fertilized rabbit eggs displayed repetitive Ca2+ rises (13 ± 1 min intervals) not observed in unfertilized eggs.
- Peak intracellular Ca2+ concentration ([Ca2+]i) averaged 466 ± 30 nM with a duration of 100 ± 3 sec.
- InsP3 and thimerosal induced Ca2+ release, with thimerosal causing larger, longer rises; heparin blocked these responses.
- Both agonists likely activate the InsP3 receptor, releasing Ca2+ from a common intracellular pool.
Conclusions:
- Rabbit eggs exhibit fertilization-induced repetitive Ca2+ rises, consistent with other mammalian species.
- Inositol 1,4,5 trisphosphate (InsP3) and thimerosal are potent stimulators of intracellular Ca2+ release in rabbit eggs.
- These agonists appear to act via the InsP3 receptor, targeting a shared intracellular Ca2+ store, highlighting a conserved mechanism in mammalian egg activation.