Activation of sea urchin eggs by a channel-forming ionophore amphotericin B

Micromolar amounts of the channel-forming ionophore amphotericin B (AMB) can activate Hemicentrotus pulcherimus eggs. Except for protein synthesis, activation by AMB was fairly normal in artificial sea water. In the case of AMB activation, it was found that external Na⁺ is necessary to initiate the activation process. External Ca²⁺, however, is not necessarily required-other than for complete fertilization membrane formation. These results suggest that AMB may induce the release of Ca²⁺ required for activation from internal calcium stock, as has been reported previously by many authors, using A 23187.