Bovine mural granulosa cells, and not the oocyte, are the major source of proteases capable of IGFBP-2 degradation.
Oocytes can regulate their own development, hence studies identifying and characterising oocyte-secreted factors are crucial to resolving the mechanisms by which oocytes can orchestrate follicular development. The insulin-like growth factor (IGF) system plays an important role during the development of a follicle; however, the regulation of IGF bioavailability is crucial throughout follicular growth. Proteolytic cleavage of the IGF/IGF binding protein (IGFBP) complex increases IGF bioavailability, hence, the production of IGFBP proteases by the oocyte and/or granulosa cells would provide a regulatory mechanism whereby they could regulate their own exposure to IGFs. The present study revealed mural granulosa cells (MGC), and not the oocyte, are the major source of proteases capable of cleaving IGFBP-2 in the developing bovine antral follicle. The addition of recombinant IGF-I or FSH had no effect in terms of modulating IGFBP-2 degradation. This work further supports the existence of a local regulatory mechanism modulating IGF bioavailability.
Walters
Kirsty A
KA
Institute of Molecular Biology, The Darwin Building, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, United Kingdom. kwalters@med.usyd.edu.au
Armstrong
David G
DG
Telfer
Evelyn E
EE
D000818:Animals; D002417:Cattle; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D006107:Granulosa Cells / Q000201:enzymology*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009865:Oocytes / Q000201:enzymology; D006080:Ovarian Follicle / Q000166:cytology / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism*
D018971:Insulin-Like Growth Factor Binding Protein 2; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone; D010447:Peptide Hydrolases