Kogiku Shiba | PubMed Health

PubMed2005

Sperm-activating peptide induces asymmetric flagellar bending in sea urchin sperm.

Speract, a sperm-activating peptide (SAP) from sea urchin eggs, induces various sperm responses including a transient increase in the intracellular Ca2+ concentration. However, it has not been clarified how speract modulates sperm motility and whether it functions as a chemoattractant. To confirm the effect of speract on sperm motility, we observed the flagellar bending response to speract in sperm of Hemicentrotus pulcherrimus, in experiments using caged speract and a lighting system for a microscope newly developed with a power LED. We found that speract induces increases in curvature of swimming paths and changes flagellar bending shape to asymmetric. These facts show that speract directly regulates flagellar motility, and suggest that speract-induced increases in intracellular Ca2+ concentration play an actual role in regulation of the flagellar movement.

Animals↗

PubMed2004

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

Speract, a sperm-activating peptide (SAP) from sea urchin eggs, increases the intracellular concentration of Ca(2+) ([Ca(2+)]i) and modulates sperm motility. We measured the initial sperm response to speract using its caged analog and observed, for the first time, a small but significant decrease in sperm [Ca(2+)]i before the increase. Both directions of the [Ca(2+)]i change were completely blocked in high K(+) seawater. Using membrane-permeant caged cyclic nucleotides (cNMP), only cGMP induced the decrease in [Ca(2+)]i although both cGMP and cAMP increased the [Ca(2+)]i. The decrease in the [Ca(2+)]i induced by cGMP was more notable following a second photolytic event, once [Ca(2+)]i had been elevated by an initial flash. This pattern of [Ca(2+)]i change was confirmed in individual sperm. These results together with pharmacological evidence suggest that the initial [Ca(2+)]i decrease is due to a Na(+)/Ca(2+) exchanger activity, stimulated by hyperpolarization mediated by K(+) efflux through cGMP-regulated K(+) channels.

1-Methyl-3-isobutylxanthine↗