The Elevation of Sperm Adenosine 3′,5′-Monophosphate Concentrations by Factors Released From Eggs Requires Calcium1

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Abstract
In the presence of seawater containing normal amounts of Ca2+ (9.1 mM) and Mg2+ (52.0 mM), theophylline (1.5 mM) caused about a 2-fold increase, factors released from eggs of the sea urchin Strongylocentrotus purpuratus a 3-fold increase and the combination of egg factors and theophylline a 17-fold increase in sea urchin sperm cyclic[c]AMP concentrations after a 1 min incubation. When Ca2+ was eliminated from the seawater, theophylline still caused a 2-fold increase, but the egg factors, in the presence or absence of theophylline, failed to elevate sperm cAMP concentrations. In contrast to the situation with Ca2+, the cAMP responses to the egg factors were not affected by the elimination of Mg2+. In Mg2+-free seawater, the divalent cation ionophore, A23187, caused marginal increases in sperm cAMP concentrations, but when tested in combination with the egg factors, it depressed the egg factor effect on sperm cAMP. Ca2+ is absolutely required for elevation of sea urchin sperm cAMP concentrations by factors released from sea urchin eggs; these factors may not cause these effects by a primary mediation of Ca2+ transport.

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