We found that the follicular wall, granulosa cells and cumulus cells contain mRNA for FSH receptor whereas oocytes do not. The mRNA of LH recpetor is only present in theca cells. IVM of COCs with bGH accelerated progression of meiosis, induced cumulus expansion and enhanced the number of blastocysts in vitro . In the cow, stimulated with gonadotropin, asynchrony between oocyte and follicle maturation was found. Interfollicular asynchrony could be reduced when the release of the preovulatory LH surge was temporarily postponed with a progestagen, resulting in prolongation of the period of follicular development preceding final maturation.
More follicles become functional with regard to oestradiol production.
Final maturation in vivo proved that operative in vitro systems are by far not optimal by producing two-fold higher hatching rates for blastocysts. While affecting transduction of the FSH signal in developing follicles for increasing oestradiol synthesis, the IGF-BP system appeared to be permissive during final maturation. Only in deviating follicles, low MW IGF-BPs were found, whereas gene expression was always present for all 4 BPs. We recently found that LH activity is essential during preovulatory development. This sign of cytoplasmic maturation is prerequisite for subsequent fertilization.