Calcium Ionophore

Calcium Ionophore(Ca2+ ionophore) is the generic name for a substance that enhances the permeability of calcium ions in the cell membrane. In ART it is used to cause the activation of the oocyte. It is used in cases of failure of conception and in severe male infertility.

Fertilization happens when each nucleus fuses with the sperm inside the oocyte.

First the sperm enters the oocyte and passes through the "shell" (transparent layer), entering the oocyte and adheres to the cell membrane. Then, a substance called PLCζ that the sperm has will increase the calcium in the oocyte. Calcium continues to spread within the oocyte, and the oocyte will activate. This wave of calcium will repeat itself, followed by a certain period of time(calcium oscillation). Various changes occur in the oocyte, two pro-nucleus(oocyte-derived genes and sperm-derived genes are in them) are formed, and finally fertilization is complete when the two are fused together.

1) Passing through the transparent layer

Enzymes (hyaluronidase) from the sperm head will leave and dissolve the transparent zone(zona pellucida), and enter inside the transparent layer (perivitelline space).

透明帯貫通

2) Membrane fusion

The sperm will adhere to the cell membrane of the oocyte. At this point, the penetration of other sperm is blocked. Oocyte activation substance (PLCζ) is released from the sperm.

膜融合

3) Oocyte activation

PLCζ causes the release of calcium from the endoplasmic reticulum of the oocyte cytoplasm.
Calcium is spread in a wave in the oocyte cytoplasm.
When the oocyte is activating during this process (calcium oscillation), it will continue until the pro-nuclear period.
During this time, the meiosis of the oocyte and the second polar body release, the collapse and re-aggregation of the sperm nuclear membrane occurs.

卵子活性化

4) 2 Pronuclear formation ˜ Before fusion

The female pro-nucleus with the genes derived from the oocytes and the male pro-nucleus with the genes derived from the sperm are formed. Finally when the two nuclei are joined then the fertilization is complete.

2前核形成~前核融合

In the case of ICSI, when the sperm is injected into the oocyte by the needle the oocyte will activate, but because PLCζ release is bypassed from the membrane fusion, an increase in calcium is required for the activation of the ovum, this might be insufficient. When this happens, calcium ionophore is key.
Calcium ionophore encourages an increase in the calcium concentration in the oocyte cytoplasm, and then induces oocyte activation after ICSI.