Changes in zona pellucida surface after in vivo and in vitro maturation ofcaprine oocytes

The zona pellucida (ZP) surface features of ovulated, inmature and in-vitro -matured goat oocytes were evaluated by scanning electron microscopy. The i n vitro maturation (IVM) process of the ZP surface of oocytes from prepuber tal and adult goats were also compared. Ovulated oocytes were collected fro m superovulated adult goats. Immature oocytes were recovered from slaughter house ovaries of prepubertal and adult goats. In-vitro-matured oocytes from adult and prepubertal goats were obtained after culture in TCM199 suppleme nted 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% CO2 in air. All oocy tes 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 acqu ired a lattice-like appearance with the outermost layer characterized by th e presence of shallower large holes (Type II ZP). A higher percentage of oo cytes showing the mature type II ZP surface was observed in ovulated than i n 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 p rocess of oocytes (immature and in-vitro-matured oocytes) from adult and pr epubertal females was compared. These results show that the morphology of t he 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 ooc ytes from adult and prepubertal goats.