Effects of IGF-I bioavailability on bovine preantral follicular development in vitro.
The aim of this study was to determine the effect of regulation of IGF-I bioavailability on preantral follicle development in vitro. Bovine preantral follicles were cultured for 6 days in serum-free medium with increasing doses of Long R3 (LR3) IGF-I (an analog with low affinity for IGF-binding proteins (IGFBPs)), or human recombinant IGF-I (hrIGF-I). Follicle diameter and estradiol production were measured every second day. On day 6, ratios of oocyte/follicle diameter and oocyte morphology were assessed by histological examination, and IGFBP-2 and -3 were detected by immunocytochemistry and in situ hybridization respectively. Both types of IGF-I increased follicle diameter in a dose-dependent manner (P < 0.05) and increased estradiol production over control levels (P < 0.05). However, follicles treated with LR3 IGF-I and the highest concentration of hrIGF-I (1000 ng/ml) had smaller oocyte/follicle ratios, and increased oocyte degeneration, compared with controls or follicles treated with physiological concentrations of hrIGF-I (P < 0.05). IGFBPs were detected in cultured preantral follicles, indicating a requirement for regulation of IGF bioavailability during the early stages of follicular development. Specifically, IGFBP-3 mRNA was found to be expressed in oocytes, and IGFBP-2 immunoreactivity was detected in oocytes and granulosa cells of cultured follicles. In summary, the regulation of IGF-I bioavailability by IGFBPs is necessary for the co-ordination of oocyte and follicle development in vitro.
Thomas
Fiona H
FH
Institute of Cell Biology, University of Edinburgh, The Darwin Building, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, UK.
Campbell
Bruce K
BK
Armstrong
David G
DG
Telfer
Evelyn E
EE
D000818:Animals; D001682:Biological Availability; D002417:Cattle; D016895:Culture Media, Serum-Free; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000032:analysis / Q000096:biosynthesis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization / Q000379:methods; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000032:analysis / Q000096:biosynthesis; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors; D046509:Tissue Culture Techniques
D016895:Culture Media, Serum-Free; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D012333:RNA, Messenger; D011994:Recombinant Proteins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I