Induction of the Acrosome Reaction in Sea Urchin Spermatozoa by the Volatile Anesthetic Halothane1

The volatile anesthetic halothane rapidly and dose-dependently induces the acrosome reaction in sperm of the sea urchin Lytechinus variegatus. The reaction occurs equally well in artificial sea water containing 10 mM Ca2+ and in low (less than 100 microM)-Ca2+ media. The anesthetic-induced acrosome reaction can be prevented by pretreating sperm with EGTA, lanthanum, or procaine. In contrast, the Ca2+ channel blockers D-600, verapamil, diltiazem, and nitrendipene do not prevent the reaction. Acrosomal processes induced by halothane are ultrastructurally identical to those induced by egg jelly, the natural inducer of the acrosome reaction. These results suggest that Ca2+ in low quantity is required for the anesthetic-induced acrosome reaction and may be derived from internal sources. Enflurane, isoflurane, and methoxyflurane also induce the acrosome reaction, indicating that volatile anesthetics may be useful in studying ion changes accompanying sperm activation.