. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 292 H. SCHUEL postulated to also act as a spermicidal agent to help prevent polyspermy (Foerder and Shapiro, 1977; Klebanoff ^/ al, 1979; Shapiro and Eddy, 1980), since H2O2 is toxic to sperm (Evans, 1947). Evidence for a peroxide-mediated block to polyspermy in sea urchins has been obtained (Boldt et al, 1981; Cobum et al, 1981). Sperm are rapidly inactivated by egg-derived H2O2. However, a peroxidase endogenous to the sperm appears to be responsible for their inactivation (Boldt, 1982; Boldt et al, 1981, 1984). Sea urchin
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 292 H. SCHUEL postulated to also act as a spermicidal agent to help prevent polyspermy (Foerder and Shapiro, 1977; Klebanoff ^/ al, 1979; Shapiro and Eddy, 1980), since H2O2 is toxic to sperm (Evans, 1947). Evidence for a peroxide-mediated block to polyspermy in sea urchins has been obtained (Boldt et al, 1981; Cobum et al, 1981). Sperm are rapidly inactivated by egg-derived H2O2. However, a peroxidase endogenous to the sperm appears to be responsible for their inactivation (Boldt, 1982; Boldt et al, 1981, 1984). Sea urchin eggs release H2O2 into the ambient sea water during the cortical reaction at fertilization (Fig. 12). The fertilizing capacity of sperm is rapidly reduced by treatment with equivalent concentrations of H2O2 (Boldt et al, 1981; Cobum et al, 1981). For example, with minimal sperm densities, 300 tiM H2O2 produces an instantaneous 35% reduction in sperm fertility which is further suppressed to a 90% reduction over five minutes (Boldt et al, 1981). The fertilizing capacity of control sperm in sea water remains constant during this period. Removal of egg-derived H2O2 by adding catalase to fertilization cultures of Arbacia produces a concentration dependent induction of polyspermy (Cobum et al, 1981; Dunham et al, 1982). Catalase does not impair elevation of the fertilization envelope. It must be added prior to completion of the cortical reaction to cause polyspermy (Fig. 13). The addition of equivalent amounts of bovine serum albumin, a non-enzymatic protein, does not cause polyspermy (Cobum et al, 1981; Schuel, 1984). Furthermore, inactivation of catalase by heating or addition of 3-amino-l,2,4-triazole, an inhibitor which binds irreversibly with the catalase-H202 300i-. //-• TIME(min.) iH Figure 12. Release of H2O2 by Stwngylocentrotus purpuratus eggs during fertilization. Eggs inseminated with a sperm density just sufficient to obtain 100% fertilization. Gametes were removed fro
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