Heavy metal chelators prolong motility and viability of sea urchin sperm by inhibiting spontaneous acrosome reactions.

A variety of heavy metal chelating agents is known to prolong the fertilizing capacity and motility of sea urchin sperm. We report here that these agents maintain fertilizing capacity by preventing acrosome reactions which occur spontaneously after dilution of sperm into seawater. These chelating agents also inhibit acrosome reactions induced by high pH or egg jelly. Since induction of the acrosome reaction leads to steps that abolish motility, specifically a massive Ca2+ uptake and concomitant acidification of the cytoplasm, motility is prolonged by these chelators. These observations also suggest that heavy metals play a role in controlling the acrosome reaction in sea urchin sperm.