The penetrability of rabbit ova treated with enzymes or anti-progesterone antibody: a probe into the nature of a mammalian fertilizin

Abstract

The acrosome reaction of rabbit spermatozoa, an essential prerequiste for penetration of the zona, occurs usually in the vicinity of the egg, suggesting that the rabbit may produce a factor akin to the 'fertilizin' of some invertebrates. Specific inactivation of such a factor should render eggs impenetrable and possibly point to the nature of a 'fertilizin' in mammals. Rabbit eggs with granulosa cells removed were treated for different periods with trypsin, chymotrypsin, neuraminidase or anti-progesterone antiserum, and then transferred alone, or together with control eggs (one group labelled with fluorescein isothiocyanate), to the oviducts of inseminated recipients. Three hours later the eggs were recovered and the experimental and control groups were compared for penetration of the vitellus and for numbers of spermatozoa within the perivitelline space or in the zona pellucida. None of these treatments affected the penetrability of the zona pellucida significantly since the number of spermatozoa within treated eggs in any one experiment was always comparable to that of untreated eggs exposed to the same fertilization environment. If there is a specific substance emanating from or present on the surface of the rabbit egg which induces the acrosome reaction, its activity seems unaffected by trypsin or chymotrypsin; the charged radicals of N-acetyl neuraminic acid or local concentrations of progesterone do not appear to be involved.

PIP: The influence of enzyme or antiprogesterone antiserum treatment on the penetrability of rabbit ova was studied. Ova were recovered from oviducts, treated for varying periods of time with either trypsin, chymotrypsin, neuraminidase or antiprogesterone antiserum, and then transferred alone, or with control ova, to the oviducts of inseminated animals. 3 hours after transfer, they were recovered and examined for penetration of the vitellus and for the number of spermatozoa present in the perivitellum space or zona pellucida. Although no vitrelline penetration was observed in ova treated with the higher concentration of neuraminidase, the number of spermatozoa passing through the zona pellucida was not affected. Trypsin, chymotrypsin, and antiprogesterone antiserum treatment had only a slight effect on spermatozoic penetration of the zona pellucida and vitellus. There was no significant difference in ova penetrability between treated and control groups. It is concluded that trypsin and chymotrypsin do not affect any possible "fertilizin-like" substance of the ovum.