The change of solubility properties of zona pellucida to proteases related to fertilizability of mouse ova in vitro.

Abstract

Zona solubility properties to proteases were found to be different depending on the surroundings in which the treatments were done. The authors found that not all mouse ova which ovulated after the usual superovulation treatment were susceptible to zona removal by proteases in modified Krebs Ringer bicarbonate medium, that this susceptibility diminished as the time between ovulation and recovery increased, and that the proportion of fertilizable ova in vitro was the same order and the same pattern as the changes of zona solubility properties. The additional treatment of the mice with PMS abolished the decline in susceptibility and fertilizability. When ova were recovered at 12 hr after HCG injection and held in culture for a further 12 hr, there was no significant decline in either variable. If ova were placed for 2 hr in sperm suspension, dissolution of the zona by protease was completely prevented but this effect was not produced by sperm-free supernatants of sperm suspension. The effect was induced sooner by in vitro capacitated spermatozoa (15 min) than by epididymal spermatozoa (45 min). The loss of dissolution susceptibility in these treatments with sperm suspension was associated with the time of sperm penetration reported in previous paper.