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Repetitive calcium transients in hamster oocytes
1Department of Physiology, Tokyo Women's Medical College Kawada-cho, Japan.
Cell Calcium
|February 1, 1991
Summary
Golden hamster oocytes exhibit cyclical calcium (Ca2+) transients during fertilization, involving both sperm-induced and internal signaling pathways. External calcium influx is crucial for sustaining these repetitive Ca2+ oscillations.
Area of Science:
- Cell Biology
- Reproductive Biology
- Biochemistry
Background:
- Fertilization triggers complex intracellular calcium (Ca2+) dynamics in oocytes.
- Understanding Ca2+ oscillations is key to comprehending early embryonic development.
Purpose of the Study:
- To investigate the mechanisms and characteristics of repetitive Ca2+ transients in golden hamster oocytes during fertilization.
- To elucidate the roles of inositol 1,4,5-trisphosphate (InsP3)-induced Ca2+ release (IICR) and Ca2+-induced Ca2+ release (CICR) in these oscillations.
Main Methods:
- Observation of Ca2+ transients in oocytes using imaging techniques.
- Experimental manipulation of intracellular Ca2+ levels via GTP gamma S and InsP3 injection.
- Assessment of the impact of external Ca2+ on Ca2+ transient frequency and amplitude.
Main Results:
- Fertilization involves propagating and synchronous Ca2+ rises.
- Unfertilized eggs show cyclic Ca2+ rises upon stimulation with GTP gamma S or InsP3.
- Both IICR and CICR contribute to Ca2+ release, with a refractory period observed.
- External Ca2+ influx is essential for sustained Ca2+ transients.
- Sperm increases egg plasma membrane permeability and CICR sensitivity.
Conclusions:
- A model of Ca2+ oscillation is proposed, involving a second messenger-controlled oscillator.
- Continuous InsP3 supply and elevated basal intracellular Ca2+ levels support IICR and CICR, facilitating Ca2+ pool re-priming.
- Protein kinase C provides tonic feedback inhibition in G-protein-mediated Ca2+ transients.