Inhibition of Chorion Expansion and Preservation of Fertility in Goldfish (Carassius auratus) Eggs by Protease Inhibitors

The in vitro effects of protease inhibitors on chorion expansion and the fertility of goldfish (Carassius auratus) eggs were investigated. Expansion of the chorion in ovulated eggs was blocked by the serine protease inhibitors benzamidine and soybean trypsin inhibitor when they were held in a goldfish Ringer solution. Eggs in which chorion expansion was inhibited retained their fertility for 30 min when held in this solution. In contrast, ovulated eggs lost their fertility in freshwater even in the presence of a protease inhibitor. The results suggest that chorion expansion and loss of fertility in water-activated goldfish eggs may involve proteolysis which was blocked by benzamidine and soybean trypsin inhibitor. Moreover, the blockage of chorion expansion may be pivotal to the preservation of fertility in eggs held in Ringer's solution with soybean trypsin inhibitor. The development of this solution provides a means to temporarily hold ovulated goldfish eggs in a viable state outside the female and will permit further studies on fertilization in this species.