Differential regulation by FSH and IGF-I of extracellular matrix IGFBP-5 in bovine granulosa cells: effect of association with the oocyte

Inhibition of insulin-like growth factor (IGF)-I induced DNA synthesis in b ovine oocyte-cumulus complexes (OCCs) caused by follicle-stimulating hormon e (FSH) has been linked to changes in the extracellular matrix which do not occur in mural granulosa cells (MGCs). We investigated regulation by IGF-I and FSH of secreted and extracellular matrix entrapped IGF-binding protein s. OCCs and MGCs from bovine ovaries were cultured in media supplemented wi th IGF-I and FSH for 24 h. Culture media and extracellular matrix were anal ysed for IGF-binding proteins by Western ligand blot and immunoblot and fou nd to contain principally IGFBP-3 and -5. The combined treatment of IGF-I a nd FSH increased the concentration of IGFBP-3 in OCC and MGC conditioned me dia by 4- and 6-fold, respectively. Treatment of OCCs and not MGCs with IGF -I and FSH together increased extracellular matrix IGFBP-5 by 2.5-fold. The differential regulation of extracellular matrix IGFBP-5 in OCCs compared t o MGCs suggest involvement of changes in the extracellular matrix brought a bout by IGF-I and FSH in overall regulation of IGF-I in the ovarian follicl e. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.