Biology of Reproduction, Vol 18, 181-185, Copyright © 1978 by Society for the Study of Reproduction

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

¹ Vanderbilt University Medical Center, Departments of Pharmacology and Physiology, Nashville, Tennessee 37232

In the presence of seawater containing normal amounts of Ca²⁺ (9.1 mM) and Mg²⁺ (52.0 mM), theophylline (1.5 mM) caused approximately 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 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 either the presence or absence of theophylline, failed to elevate sperm cyclic AMP concentrations. In contrast to the situation with Ca²⁺, the cyclic AMP 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 cyclic AMP concentrations, but when tested in combination with the egg factors, it depressed the egg factor effect on sperm cyclic AMP. These results demonstrate that Ca²⁺ is absolutely required for elevation of sea urchin sperm cyclic AMP concentrations by factors released from sea urchin eggs, and suggest that these factors do not cause these effects by a primary mediation of Ca²⁺ transport.

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ACKNOWLEDGMENTS The authors wish to thank Ms. Helen E. Watkins and Ms. Marvist A. Parks for their excellent technical assistance.