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Non-specific currents at fertilisation in sea urchin oocytes
M L De Simone1, L Grumetto, E Tosti
1Università Federico II, Naples, Italy.
Zygote (Cambridge, England)
|July 4, 1998
Summary
Fertilizing sperm activate sea urchin oocytes by triggering a calcium-dependent inward ion current. This ion current causes membrane depolarization and increased conductance during fertilization.
Area of Science:
- Reproductive biology
- Cellular physiology
- Ion channel research
Background:
- Fertilization in sea urchins involves a rapid electrical response in the oocyte.
- Understanding the ion flux during fertilization is crucial for comprehending early developmental events.
Purpose of the Study:
- To investigate the ionic basis of the electrical changes occurring in sea urchin oocytes upon sperm activation.
- To characterize the nature and ionic dependency of the inward current triggered by fertilization.
Main Methods:
- Whole-cell voltage-clamp technique applied to sea urchin oocytes.
- Measurement of membrane potential, conductance, and ion currents during fertilization.
- Inositol triphosphate injection and calcium chelation (BAPTA) to probe ion dependency.
Main Results:
- Sperm fertilization induced a significant inward current (-521 +/- 56.7 pA) in oocytes.
- Simultaneous plasma membrane depolarization and increased conductance (23.4 to 40.6 nS) were observed.
- The activation current was identified as non-specific and calcium-dependent, as evidenced by inositol triphosphate-induced currents and BAPTA inhibition.
Conclusions:
- The fertilizing spermatozoon triggers a calcium-dependent, non-specific inward ion current in sea urchin oocytes.
- This current plays a key role in the electrical activation of the oocyte during fertilization.
- Findings provide insights into the molecular mechanisms underlying gamete fusion and early embryonic signaling.