Possible involvement of insulin-like growth factor-I in mediating the stimulatory effect of recombinant bovine growth hormone on maturation of bovine oocytes in vitro
1998
Iga, K. (Okayama Univ. (Japan). Faculty of Agriculture) | Niwa, K. | Bartke, A.
The present study was undertaken to determine whether insulin-like growth factor-I (IGF-I) is involved in mediating the stimulatory effects of growth hormone (GH) on nuclear maturation of bovine oocytes in vitro and subsequent embryonic development after in vitro fertilization. When cumulus-oocyte complexes (COCs) or cumulus-free oocytes were cultured in modified Medium 199 supplemented with 0-100 ng/ml recombinant human IGF-I (rhIGF-I), the proportion of COCs with slight cumulus expansion was increased with increasing concentration of rhIGF-I after 12 and 24 h of culture. Nuclear maturation of oocytes to the metaphase II (M-II) stage was promoted by rhIGF-I only in COCs, with higher proportions of M-II oocytes at 10-100 ng/ml (74 +- 3 - 76 +- 3%) than at 0-1 ng/ml (53 +- 4 - 61 +- 1%) after 24 h of culture. When COCs were cultured in the presence of 100 ng/ml rhIGF-I or 10 ng/ml recombinant bovine GH(rbGH) and/or anti-IGF-I antibody (Ab) for 24 h, the proportion of oocytes reaching the M-II stage was higher with rhIGF-I (73 +- 2%) or rbGH (74 +- 1%) than in the absence of these additives (54 +- 3%), in Ab alone (54 +- 3%), or with IGF-I or GH in combination with Ab (54 +- 3 - 58 +- 1%). The inhibition of the stimulatory effects of rbGH on nuclear maturation by Ab was dose-dependent. After in vitro maturation and fertilization, no differences were observed in the penetration rate (75 +- 3 - 77 +- 6%), pronuclear formation (56 +- 3 - 64 +- 10%) and polyspermy (28 +- 4 - 36 +- 5%) at 8 h post-insemination among cumulus enclosed oocytes cultured in the presence of different additives. When the oocytes were cultured in a chemically defined medium starting from 8 h after insemination, 20 +- 1 - 26 +- 2% of oocytes developed to the - morula stage 144 h post-insemination without difference among different additives during maturation
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