Anion Channel Blockers Inhibit the Acrosome Reaction of Echinoderm Sperm: anion channel blocker/acrosome reaction/acid release/stafish/sea urchin

Two types of anion channel blockers, SITS (4‐acetamide‐4‘‐isothiocyanostilbene‐2,2′‐disulfonic acid) and DIDS (4,4′‐diisothiocyanostilbene‐2, 2’‐disulfonic acid), inhibited jelly‐induced acrosorne reaction in starfish and sea urchin. In starfish sperm, both of the blockers reversibly inhibited the formation of acrosomal process but they had no effect on either the acrosomal exocytosis or acid release from the sperm. Complete acrosome reaction occurred even in Cl⁻‐ and SO₄²⁻‐free artificial seawater whereas HCO₃⁻was required for the acrosomal exocytosis. Importance of anion transport in acrosome reaction is discussed.