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Related Experiment Videos

A sea urchin egg jelly peptide induces a cGMP-mediated decrease in sperm intracellular Ca(2+) before its increase.

Takuya Nishigaki1, Christopher D Wood, Yoshiro Tatsu

  • 1Department of Developmental Genetics and Molecular Physiology, Institute of Biotechnology, UNAM, Cuernavaca, Morelos 62210, Mexico. takuya@ibt.unam.mx

Developmental Biology
|July 30, 2004
PubMed
Summary
This summary is machine-generated.

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Speract initially decreases sea urchin sperm intracellular Ca(2+) before increasing it, a novel finding impacting sperm activation. This calcium change is mediated by cyclic GMP and potassium channels.

Area of Science:

  • Marine Biology
  • Sperm Physiology
  • Cellular Signaling

Background:

  • Speract, a sperm-activating peptide (SAP), is known to increase intracellular calcium ([Ca(2+)]i) in sea urchin sperm, modulating motility.
  • The precise initial changes in [Ca(2+)]i upon speract stimulation have not been fully elucidated.

Purpose of the Study:

  • To investigate the initial changes in intracellular calcium ([Ca(2+)]i) in sea urchin sperm in response to speract.
  • To identify the signaling pathways and ion transport mechanisms responsible for the observed calcium dynamics.

Main Methods:

  • Utilized caged analogs of speract and cyclic nucleotides (cGMP, cAMP) to precisely control their release within sperm.
  • Measured rapid changes in intracellular calcium ([Ca(2+)]i) using fluorescence microscopy.

Related Experiment Videos

  • Employed high potassium seawater and pharmacological agents to probe ion channel and exchanger activity.

    • Main Results:

    • Observed a novel, small, but significant initial decrease in [Ca(2+)]i preceding the expected increase upon speract stimulation.
    • Demonstrated that this initial [Ca(2+)]i decrease was blocked in high K+ seawater and could be induced by cGMP but not cAMP.
    • Evidence suggests the decrease is mediated by Na+/Ca(2+) exchanger activity, stimulated by hyperpolarization via cGMP-regulated K+ channels.

    Conclusions:

    • The initial response of sea urchin sperm to speract involves a transient decrease in [Ca(2+)]i, contrary to previous assumptions.
    • This initial calcium decline is regulated by cyclic GMP and involves K+ efflux and Na+/Ca(2+) exchange.
    • These findings provide new insights into the complex signaling mechanisms governing sperm activation and motility.