AbstractSea urchins have elaborated multiple defenses to assure monospermic fertilization. In this work, we have concentrated on a study of the mechanism(s) by which hydrogen peroxide (H2O2) prevents polyspermy inArbacia punctulata. We found that it is not H2O2but probably hypochlorous acid/hypochlorite (HOCl/OCl−) derived from H2O2that is toxic to the supernumerary sperm. The spermicidal activity of H2O2is potentiated by at least one order of magnitude by cupric ions (Cu2+). This increased toxicity is not due to the formation of hydroxyl radicals (·OH) because ·OH scavengers did not counteract the activity of Cu2+. More‐over, substitution of Cu2+by ferrous ions (Fe2+), which are known to cause formation of ·OH from H2O2, had no effect on fertilization even at 102−103times higher concentrations. In contrast, 3‐amino‐1,2,4‐triazole (AT), an HOCl/OCl−scavenger, totally reversed the toxic effects of Cu2+. Furthermore, we found that HOCl/OCl−is generated in solutions of H2O2and Cu2+in the presence of 0.5 M NaCl and that its accumulation is abolished by AT. Thus it is possible that the antifertility properties of copper are due to its ability to mediate formation of HOCl/OCl−. HOCl/OCl−generated by Cu2+from H2O2and Cl−, a low concentration of exogenously added HOCl/OCl−, or increased concentrations of H2O2has similar inhibitory effects on the fertilization process in sea urchins. Therefore, we suggest that polyspermy is prevented by the action of a myeloperoxidase that affects the formation of HOCl/OCl−from the Cl−present in sea water through reaction with H2O2generat
展开▼
