Maturation-associated changes in the rat zona pellucida.
Rat follicular oocytes, arrested at prophase I, cannot be fertilized in vitro. This capacity is acquired following resumption of meiosis and a series of changes involving both the oocyte and the cumulus cells surrounding it. Oocytes exposed to sperm at different hours before ovulation show a gradual increase in the permeability of their zona pellucida (ZP). Our study examined whether the ZP, in response to the physiological stimulus for maturation and concomitant with the other oocyte--cumulus components, undergoes maturational changes. Two ZP characteristics were assessed, sensitivity to proteolysis and sperm binding. ZP surrounding oocytes and eggs were collected from five sources: 1) germinal vesicle (GV)-intact oocytes, 2) preovulatory eggs, 3) ovulated eggs isolated from oviducts of immature females, 4) fertilized eggs, 5) ovulated eggs isolated from oviducts of mature females. All ZP surrounding oocytes/eggs from groups 1-5 were dissolved by trypsin. When solubility by pronase and alpha-chymotrypsin was examined, a large variation between groups was found. All ZP from group 2 were dissolved by 0.001% pronase, compared to 0% solubility in group 4. Only 10% of the ZP surrounding GV-intact oocytes (group 1) were dissolved by this enzyme, compared to 82% in group 3. Solubility in 0.01% alpha-chymotrypsin showed a similar pattern. Capacitated sperm were incubated with eggs from groups 1 and 3. The number of sperm binding to ZP in group 3 was repeatedly higher than that in group 1. In both tests it was found that the ZP surrounding the mature eggs differ in their characteristics from ZP of GV-intact oocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
Rufas
O
O
Department of Embryology and Teratology, Sackler School of Medicine, Tel Aviv University, Israel.
Shalgi
R
R
D000818:Animals; D002918:Chymotrypsin / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro; D006821:Hyaluronoglucosaminidase / Q000494:pharmacology; D008297:Male; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D009866:Oogenesis / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility; D013094:Spermatozoa / Q000502:physiology; D014357:Trypsin / Q000494:pharmacology; D015044:Zona Pellucida / Q000187:drug effects / Q000502:physiology*
D006821:Hyaluronoglucosaminidase; D002918:Chymotrypsin; D014357:Trypsin