Insulin-like growth factors (IGFs) block FSH-induced proteolysis of IGF-binding protein-5 (BP-5) in cultured rat granulosa cells

Paul J. Fielder, Hung Pham, Eli Y. Adashi, Ronald (Ron) Rosenfeld

Research output: Contribution to journalArticle

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Abstract

Rat granulosa cells (GC), in vitro, express IGFBPs under the influence of both FSH and IGF-I. The major IGFBP produced by GC is a 28-29 K IGFBP, presumed to be IGFBP-5. When GC-conditioned medium (GC-CM) was assessed by Western Ligand Blotting (WLB), FSH appeared to decrease IGFBP-5, whereas IGF-I appeared to increase IGFBP-5 and to partially block the effects of FSH treatment. When GC-CM from FSH-treated cells was incubated with pure IGFBP-4 and IGFBP-5, the amount of IGFBP-5 (measurable by WLB) was decreased. Similarly, when GC-CM from FSH-treated cells was incubated with iodinated IGFBP-4 and IGFBP-5, IGFBP-5 (but not IGFBP-4) was proteolyzed into fragments of approximately 18 and 14 K. The ability of FSH-treated GC-CM to proteolyze IGFBP-5 was reduced by the addition of IGF-I to the reaction mixture. When the IGFBPs in GC-CM were evaluated by affinity crosslinking, GC-CM from control cultures contained one band with an apparent Mr of approximately 34 K, whereas GC-CM from FSH-treated cultures displayed a decrease in the intensity of the 34 K band, as well as a new band of approximately 24 K. These data suggest that rat GC cells produce an FSH-inducible IGFBP-5 protease activity, and reveal that the ability of this protease to cleave IGFBP-5 is blocked by IGFs.

Original languageEnglish (US)
Pages (from-to)415-418
Number of pages4
JournalEndocrinology
Volume133
Issue number1
StatePublished - Jul 1993
Externally publishedYes

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Insulin-Like Growth Factor Binding Protein 5
Granulosa Cells
Somatomedins
Proteolysis
Insulin-Like Growth Factor Binding Proteins
Insulin-Like Growth Factor Binding Protein 4
Gonadotrophs
Insulin-Like Growth Factor I
Peptide Hydrolases
Western Blotting
Ligands
Conditioned Culture Medium

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Insulin-like growth factors (IGFs) block FSH-induced proteolysis of IGF-binding protein-5 (BP-5) in cultured rat granulosa cells. / Fielder, Paul J.; Pham, Hung; Adashi, Eli Y.; Rosenfeld, Ronald (Ron).

In: Endocrinology, Vol. 133, No. 1, 07.1993, p. 415-418.

Research output: Contribution to journalArticle

Fielder, Paul J. ; Pham, Hung ; Adashi, Eli Y. ; Rosenfeld, Ronald (Ron). / Insulin-like growth factors (IGFs) block FSH-induced proteolysis of IGF-binding protein-5 (BP-5) in cultured rat granulosa cells. In: Endocrinology. 1993 ; Vol. 133, No. 1. pp. 415-418.
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abstract = "Rat granulosa cells (GC), in vitro, express IGFBPs under the influence of both FSH and IGF-I. The major IGFBP produced by GC is a 28-29 K IGFBP, presumed to be IGFBP-5. When GC-conditioned medium (GC-CM) was assessed by Western Ligand Blotting (WLB), FSH appeared to decrease IGFBP-5, whereas IGF-I appeared to increase IGFBP-5 and to partially block the effects of FSH treatment. When GC-CM from FSH-treated cells was incubated with pure IGFBP-4 and IGFBP-5, the amount of IGFBP-5 (measurable by WLB) was decreased. Similarly, when GC-CM from FSH-treated cells was incubated with iodinated IGFBP-4 and IGFBP-5, IGFBP-5 (but not IGFBP-4) was proteolyzed into fragments of approximately 18 and 14 K. The ability of FSH-treated GC-CM to proteolyze IGFBP-5 was reduced by the addition of IGF-I to the reaction mixture. When the IGFBPs in GC-CM were evaluated by affinity crosslinking, GC-CM from control cultures contained one band with an apparent Mr of approximately 34 K, whereas GC-CM from FSH-treated cultures displayed a decrease in the intensity of the 34 K band, as well as a new band of approximately 24 K. These data suggest that rat GC cells produce an FSH-inducible IGFBP-5 protease activity, and reveal that the ability of this protease to cleave IGFBP-5 is blocked by IGFs.",
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