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Calcium elevation in sheep cumulus-oocyte complexes after luteinising hormone stimulation
M Mattioli1, L Gioia, B Barboni
1Istituto di Fisiologia Veterinaria, Facoltà di Medicina Veterinaria, Università degli Studi di Teramo, Italy.
Molecular Reproduction and Development
|June 11, 1998
Summary
Luteinizing hormone (LH) triggers calcium (Ca2+) increases in cumulus cells, which then signal the oocyte. This calcium transfer, crucial for oocyte maturation, occurs via gap junctions between cells.
Area of Science:
- Reproductive Biology
- Cell Signaling
- Endocrinology
Background:
- Cumulus-oocyte complexes (COCs) are essential for female reproduction.
- Luteinizing hormone (LH) surge triggers final oocyte maturation.
- Intracellular calcium (Ca2+) dynamics are critical for cellular processes.
Purpose of the Study:
- To investigate Ca2+ level changes in COCs upon exposure to LH.
- To understand the role of cumulus cells in mediating LH signaling to the oocyte.
Main Methods:
- COCs were loaded with Ca2+-sensitive dyes (FLUO-3AM in cumulus cells, FLUO-3 in the oocyte).
- Intracellular Ca2+ levels were measured after LH exposure.
- Effects of verapamil, manganese chloride, and mechanical uncoupling were assessed.
Main Results:
- LH induced rapid intracellular Ca2+ rises in cumulus and corona radiata cells.
- Ca2+ elevations were observed throughout the cumulus mass, indicating widespread LH receptors.
- A delayed Ca2+ elevation occurred in the oocyte, originating from the cortex.
- LH-induced Ca2+ rise was not blocked by verapamil or manganese chloride.
- Mechanical uncoupling prevented the oocyte's Ca2+ response.
Conclusions:
- Cumulus corona cells transduce the LH signal by increasing intracellular Ca2+.
- This Ca2+ signal is rapidly transferred to the oocyte via gap junctions.
- The transfer may involve direct Ca2+ diffusion or IP3 from cumulus cells to the oocyte.