Effects of Epidermal Growth Factor, Insulin Like Growth Factor-I and Insulin on Meiotic Maturation of Bovine Denuded Oocytes

ウシ裸化卵子の成熟に及ぼす成長因子(EGF, IGF-I, インスリン)の影響

Anas Mohamed-Kheir Idris

Elmileik Abdalla

Maeda Teruo

Terada Takato

Journal of mammalian ova research = 日本哺乳動物卵子学会誌

This study was carried out to examine whether EGF, IGF-I and insulin could directly modify the meiotic maturation of bovine denuded oocytes in vitro, and to see whether the stimulatory effect of EGF on bovine oocyte meiotic maturation is mediated through the tyrosine kinase pathway. In the first three experiments, cumulus-oocyte complexes (COCs) were removed from their cumulus cells and the denuded oocytes were cultured in vitro with various concentrations of EGF, IGF-1 and insulin. Nuclear maturation was examined after 24 h of culture. EGF, IGF-1 as well as insulin effectively increased the proportion of oocytes developed to the metaphase II stage. The higher rates of MII oocytes were achieved with 50 ng/ml EGF (69.4%), 100 ng/ml IGF-1 (66.1%) or 5 μg/ml insulin (63.1%) compared to about 48 to 54% in the controls. In experiment 4, whereas EGF significantly (p<0.05) increased the proportion of MII oocytes for denuded oocytes derived from the collected COCs, it had no stimulatory effect on MII formation of oocytes found cumulus-free or denuded at the time of aspiration. In experiment 5, with erbstatin, a specific tyrosine kinase inhibitor, the stimulatory effect of EGF on meiotic maturation of denuded oocytes was abolished. These results indicate that EGF, IGF-I and insulin could directly stimulate meiotic maturation of bovine denuded oocytes removed from the surrounding cumulus cells after oocyte collection. Moreover, the results also suggest that the stimulatory effect of EGF on bovine denuded oocyte meiotic maturation is mediated by the tyrosine kinase signal transduction pathway.

ウシの卵巣から採取した卵丘細胞卵子複合体から卵丘細胞を除去した裸化卵子を種々の濃度の成長因子(EGF, IGF-I, インスリン)を添加した培地で24時間培養した. いずれの成長因子を添加した場合にも無添加の対照区に比べて有意に高い成熟卵率が得られた. 卵巣から採取する時に既に裸化していた卵子の成熟卵率においては, 培地にEGFを添加した影響は認められなかった. さらに, 卵巣から採取した後に裸化させた卵子を, EGF添加培地およびEGFとerbstatin(チロシンキナーゼ・インヒビター)とを添加した培地で24時間培養した時には, 裸化卵子におけるEGFの成熟促進作用がerbstatinにより打ち消された. 以上の結果から, ウシ卵子の成熟はEGF, IGF-Iおよびインスリン等の成長因子により直接的に影響を受けること及び成長因子の成熟促進作用は卵子のチロシンキナーゼ情報伝達系を介していることが推察された.

EGF

IGF-I

Insulin

Meiotic maturation

Bovine oocytes

インスリン

ウシ卵子

減数分裂

Zoology [ 480 ]

eng

日本哺乳動物卵子学会

[ISSN] 1341-7738

[DOI] 10.1274/jmor.15.179

[NCID] AN10548943

[DOI] http://dx.doi.org/10.1274/jmor.15.179