title: Copper ions and hydrogen peroxide form hypochlorite from NaCl thereby mimicking myeloperoxidase.
abstract: Sea 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 in Arbacia punctulata. We found that it is not H2O2 but probably hypochlorous acid/hypochlorite (HOCl/OCl-) derived from H2O2 that is toxic to the supernumerary sperm. The spermicidal activity of H2O2 is 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+. Moreover, substitution of Cu2+ by ferrous ions (Fe2+), which are known to cause formation of .OH from H2O2, had no effect on fertilization even at 10(2)-10(3) times higher concentrations. In contrast, 3-amino-1,2,4-triazole (AT), and HOCl/OCl- scavenger, totally reversed the toxic effects of Cu2+. Furthermore, we found that HOCl/OCl- is generated in solutions of H2O2 and 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 H2O2 and Cl-, a low concentration of exogenously added HOCl/OCl-, or increased concentrations of H2O2 has 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 H2O2 generated by the newly fertilized egg.
mesh_terms: D000640:Amitrole / Q000494:pharmacology; D003300:Copper / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006997:Hypochlorous Acid / Q000378:metabolism*; D008297:Male; D010063:Ovum / Q000187:drug effects; D009195:Peroxidase / Q000378:metabolism*; D012617:Sea Urchins; D012965:Sodium Chloride / Q000378:metabolism*; D013094:Spermatozoa / Q000187:drug effects; D013654:Taurine / Q000378:metabolism
chemical_list: D013654:Taurine; D012965:Sodium Chloride; D006997:Hypochlorous Acid; D003300:Copper; D006861:Hydrogen Peroxide; D009195:Peroxidase; D000640:Amitrole