Inhibition of the acrosome reaction of sea urchin spermatozoa by a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7).

A calmodulin antagonist, W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide), inhibited induction of the acrosome reaction of sea urchin spermatozoa by egg jelly at 20-50 microM, but W-5 did not. The latter, a chlorine-deficient derivative of W-7, has a lower affinity for calmodulin than does W-7. These results suggest that a Ca2+-calmodulin-dependent process plays an important role in the triggering process of the acrosome reaction of sea urchin spermatozoa.