Differential Effects of the Egg Jelly Molecules FSG and SAP-I on Elevation of Intracellular Ca and pH in Sea Urchin Spermatozoa: (FSG/SAP-I/[Ca ] /pH ).

We examined the effects of two egg jelly components, a fucose sulfate glycoconjugate (FSG) and sperm-activating peptide I (SAP-I: Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly), on the intracellular pH (pH ) and Ca ([Ca ] ) of spermatozoa of the sea urchin Hemicentrotus pulcherrimus. FSG and/or SAP-I induced elevations of [Ca ]; and pH in the spermatozoa at pH 8.0. At pH 8.0, a second addition of FSG did not induced further elevation of the [Ca ] or pH of spermatozoa treated with FSG, but addition or FSG after SAP-I or of SAP-I after FSG induced further increases of [Ca ] and pH , At pH 6.6, FSG and/or SAP-I did not induce significant elevation of the [Ca ] , although SAP-I elevated the pH , its half-maximal effective concentration being 10 to 100 pM. At pH 8.0, tetraethyl-ammonium, a voltage-sensitive K -channel blocker, inhibited induction of the acrosome reaction and elevations of [Ca ] and pH by FSG, but did not affect those by SAP-I. These results suggest that FSG and SAP-I activate different Ca and H transport systems.