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Updated: Jul 27, 2025
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Medium-throughput Screening Assays for Assessment of Effects on Ca2+-Signaling and Acrosome Reaction in Human Sperm
Published on: March 1, 2019
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Calcium and Cyclic AMP Mediate Sperm Activation, but Ca
Manabu Yoshida1, Kazuo Inaba1, Katsumi Ishida2
1Misaki Marine Biological Station, School of Science, University of Tokyo, Misaki, Miura, Kanagawa 238-02, Japan.
Development, Growth & Differentiation
|June 7, 2023
Summary
Sperm-activating and -attracting factor (SAAF) requires calcium ions to activate sperm motility and cAMP synthesis. Calcium influx through T-type channels triggers activation, while calcium alone mediates sperm chemotaxis in Ciona.
Area of Science:
- Marine Biology
- Reproductive Biology
- Biochemistry
Background:
- Sperm activation and chemotaxis are crucial for fertilization.
- Ascidian sperm-activating and -attracting factor (SAAF) plays a role in reproduction.
- The specific mechanisms of SAAF action were not fully understood.
Purpose of the Study:
- To elucidate the role of calcium ions and cAMP in SAAF-mediated sperm activation.
- To investigate the ion channels involved in sperm activation and chemotaxis.
- To understand the signaling pathways triggered by SAAF in Ciona savignyi.
Main Methods:
- Partial purification of SAAF from ascidian egg seawater using ethanol extraction and a chloroform-water two-phase system.
- Sperm motility and cAMP level assays in calcium-free seawater (CaFSW) and artificial seawater with varying calcium concentrations.
- Pharmacological inhibition studies using T-type and L-type calcium channel antagonists (flunarizine).
- Chemotaxis assays using glass capillaries containing SAAF.
Main Results:
- SAAF activated sperm motility and cAMP synthesis only in the presence of Ca2+.
- Flunarizine (T-type Ca2+ channel antagonist) inhibited SAAF-induced sperm activation.
- L-type Ca2+ channel antagonists had no effect on SAAF-induced activation.
- Theophylline (phosphodiesterase inhibitor) induced sperm activation and increased cAMP in CaFSW without SAAF.
- Theophylline-activated sperm showed chemotaxis toward SAAF only upon addition of Ca2+.
Conclusions:
- Sperm activation by SAAF is dependent on Ca2+ influx through T-type Ca2+ channels, leading to increased intracellular cAMP levels.
- Calcium ions alone are sufficient to mediate chemotaxis towards SAAF in Ciona sperm.
- SAAF utilizes a distinct signaling pathway involving calcium and cAMP for reproductive processes.
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