Changes in Intracellular Concentrations of Cyclic Nucleotides during the Initiation Process of Starfish Sperm Motility

Abstract
Changes in the intracellular concentrations of cyclic nucleotides during the initiation of starfish sperm motility were examined. The intracellular concentration of cGMP decreased just after dilution of sperm with sea water, whereas that of cAMP increased concomitant with initiation of sperm motility. In acidic sea water, the intracellular concentration of cGMP decreased but no increase in that of cAMP was observed and sperm remained immotile. The presence of a phosphodiesterase inhibitor enhanced the rate of increase in the intracellular concentration of cAMP and the sperm motility. These results indicate that cAMP is involved in the initiation sperm motility in starfish.