The effects of IGF-I on bovine follicle development and IGFBP-2 expression are dose and stage dependent.
This study aimed to determine the effect of insulin-like growth factor-I (IGF-I) on early antral bovine follicular development, and the expression of insulin-like growth factor-binding protein-2 (IGFBP-2). Antral follicles separated into three different size groups were cultured for 6 days in medium supplemented with either a low (10 ng/ml) or high (1 microg/ml) dose of human recombinant IGF-I. Oestradiol production by follicles in all size ranges, cultured in the presence of the high concentration of IGF-I, significantly increased by day 6 (P < 0.05). Follicles in the smallest size range, 165-215 microm, cultured in a high dose of IGF-I, were found to be significantly increased in size (P < 0.01). Oocyte health of the largest follicles (281-380 microm) was significantly improved by the addition of IGF-I to the culture medium. mRNA expression of IGFBP-2 was decreased in the granulosa cells of follicles, size range 216-280 microm, cultured with a high dose of IGF-I (P < 0.05). Granulosa cells (P < 0.05) and oocytes (P < 0.01) of the largest follicles (281-380 microm) showed a decrease in IGFBP-2 expression (protein) when cultured in the control and low-IGF-I treatment groups. Therefore, the response of a bovine follicle to IGF-I is both dose and stage dependent. This work supports a role for IGF-I in modulating somatic and germ-cell maturation and development in early antral follicles. Furthermore, the inverse relationship between the level of IGF-I stimulation and IGFBP-2 expression suggests a local regulatory system modulating IGF-I availability.
Walters
Kirsty A
KA
Institute of Cell and Molecular Biology, Darwin Building, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, UK.
Binnie
John P
JP
Campbell
Bruce K
BK
Armstrong
David G
DG
Telfer
Evelyn E
EE
D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000032:analysis / Q000096:biosynthesis; D005260:Female; D006107:Granulosa Cells / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects; D009866:Oogenesis / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D013268:Stimulation, Chemical; D046509:Tissue Culture Techniques
D018971:Insulin-Like Growth Factor Binding Protein 2; D012333:RNA, Messenger; D011994:Recombinant Proteins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I