Influence of epidermal growth factor on mammalian oocyte maturation via tyrosine-kinase pathway

Epidermal growth factor (EGF) has been reported to promote different functi ons in mammalian ovaries, including oocyte maturation. The aim of the prese nt study was to establish: that EGF influences oocyte maturation in ovine a nd equine, that a tyrosine kinase-dependent intracellular mechanism mediate s EGF effect and, that EGF-R receptor is detectable in ovarian follicles by immunohistochemistry methods. Selected ovine and equine oocytes were aspir ated from 2-5 mm (ovine) or 25 mm (equine) follicles and cultured in TCM 19 9 for 22 (ovine) or 36 hours (equine). They are then subjected to culture w ith EGF and two specific tyrosine-kinase inhibitors (TKIs, tyrphostins A-23 y A-47). Maturation was determined as the percentage of oocytes at metapha se II stage after culture. Treatments with EGF significantly increased inci dences of metaphase II stage compared to controls (86.2% vs. 55% and 70.4% vs. 22.5% in ovine and equine oocytes, respectively). Tyrphostins A-23 and A-47 were effective in suppressing EGF-effect on oocytes. EGF-receptor was localized in follicles, being more prominent in cumulus and granulosa cells . These results confirm that EGF has a physiological role in the regulation of oocyte maturation via tyrosine-kinase pathway.