Changes in zona pellucida surface after in vivo and in vitro maturation of caprine oocytes

The zona pellucida (ZP) surface features of ovulated, inmature and in-vitro-matured goat oocytes were evaluated by scanning electron microscopy. The in vitro maturation (IVM) process of the ZP surface of oocytes from prepubertal and adult goats were also compared. Ovulated oocytes were collected from superovulated adult goats. Immature oocytes were recovered from slaughterhouse ovaries of prepubertal and adult goats. In-vitro-matured oocytes from adult and prepubertal goats were obtained after culture in TCM199 supplemented with 20% oestrous goat serum + 10 mu g/ml FSH + 10 mu g/ml LH + 1 mu g/ml estradiol 17 beta for 27 h at 38.5 degrees C in 5% CO(2) in air. All oocytes were fixed in 2.5% glutaraldehyde and postfixed in 1% osmium tetroxide. Before IVM, the ZP surface of immature oocytes showed a rough surface with tight holes (Type I ZP). After the maturation process, the ZP surface acquired a lattice-like appearance with the outermost layer characterized by the presence of shallower large holes (Type II ZP). A higher percentage of oocytes showing the mature type II ZP surface was observed in ovulated than in in-vitro-matured oocytes (82.6 versus 56.7%, respectively, p < 0.05). No significant differences were observed in ZP surface features when the IVM process of oocytes (immature and in-vitro-matured oocytes) from adult and prepubertal females was compared. These results show that the morphology of the ZP surface is related to the oocyte maturity in caprine. The IVM process gives rise to an adequate and similar development of the ZP surface in oocytes from adult and prepubertal goats.