Extreme Toxicity of Ethanol During Activation of Sea Urchin Eggs: (ethanol toxicity/ionophore A23187/parthenogenesis/Strongylocentrotus purpuratus/K -permeability).

We have examined the effects of ethanol on early fertilization events and later development in the sea urchin Strongylocentrotus purpuratus. Eggs can still be fertilized in ethanol concentrations as high as 480 mM (2.0%); egg cytolysis was rapidly observed postinsemination in 50% of the cells at 220 mM ethanol. Yet, sperm motility was essentially normal in 250 mM ethanol; 940 mM ethanol was required to affect a 50% reduction. To determine the effect of ethanol on K -efflux from eggs induced by fertilization, we used parthenogenetic activation induced by the Ca -ionophore A23187. Surprisingly, ethanol at only 0.2 mM caused an abnormal K -efflux, but only when added between 1 and 3 min after induction of activation. The K -efflux rates of unfertilized eggs were not influenced by up to 730 mM ethanol. Finally, normal embryonic development through the mesenchyme blastula stage was observed in egg suspensions which were treated for 30 min with ethanol concentrations as high as 240 mM, but washed with normal seawater prior to insemination. Normal plutei were obtained from cultures which were continuously cultured in 24 mM ethanol from 15 min postinsemination. We conclude that an extreme ethanol sensitivity of embryogenesis is apparent only during the cortical reaction.