A factor potentiating serotonin in the induction of germinal vesicle breakdown in surf clam oocytes

Simultaneous addition of an aliquot of body fluid obtained from the surf clam, Spisula solidissima, enhanced oocyte germinal vesicle breakdown induced with serotonin but not with KCl. When the body fluid and serotonin were added sequentially to the oocytes, potentiation did not occur. Body fluids of both males and females were effective at a 200-fold dilution. The factor is stable when treated with heat, acid, base, trypsin and pronase. It is hydrophobic and not dialyzable through tubing with a molecular weight cutoff of 1000 daltons. The factor is probably not a protein.