A combination of EGF and IGF-I accelerates the progression of meiosis in bovine follicular oocytes in vitro and fetal calf serum neutralizes the acceleration effect

The effects of a combination of EGF and IGF-I (GFs) on the progress of meio sis and on their developmental competence were examined in cumulus-enclosed bovine oocytes. Exposure to GFs in serum-free, 0.3% PVP-containing maturat ion medium significantly (P<0.05) increased the frequency of oocytes with t he first polar body (PB) at 16 h of culture and decreased those with PB at 20 h. The cleavage rates of PB-extruded oocytes after fertilization were no t affected by treatment of GFs during maturation culture, and blastocyst yi eld was not improved by GFs treatment. Although replacement of PVP from GFs -containing medium with fatty acid-free BSA did not affect the timing of PB extrusion, replacement with 10% FCS neutralized the acceleration effects o f GFs. Replacement for macromolecule in maturation medium did not improve b lastocyst yield of PB-extruded oocytes after fertilization. These results i ndicate that the progression of meiosis in bovine oocytes with cumulus cell s is accelerated by exposure to GFs in serum-free maturation medium but the ir developmental competence is not improved, and that the acceleration effe cts on the progress of meiosis is neutralized by the presence of FCS in mat uration medium with no improvement of developmental competence after in vit ro fertilization. (C) 2000 by Elsevier Science Inc.