Endogenous insulin-like growth factor-I is obligatory for stimulation of rat inhibin alpha-subunit expression by follicle-stimulating hormone.
Biol Reprod
; 58(1): 219-25, 1998 Jan.
Article
en En
| MEDLINE
| ID: mdl-9472944
Insulin-like growth factor-I (IGF-I) is essential for FSH-dependent steroidogenesis by rat granulosa cells (GC), but whether IGF-I is required for other FSH-dependent functions is unknown. To investigate the role of IGF-I in the mechanisms of FSH-stimulated inhibin alpha-subunit (Inh-alpha) production, rat GC were cultured with FSH, IGF-I, insulin-like growth factor-binding protein (IGFBP)-4, IGFBP-5, and/or anti-IGF-I antibody. Inh-alpha protein and mRNA levels were measured in conditioned medium and cells by Western immunoblotting and Northern analysis, respectively. Inh-alpha expression was increased by FSH (3.5-fold) and IGF-I (2.5-fold), and the effects were dose and time dependent. FSH stimulation of Inh-alpha was attenuated by IGFBP-4 or -5 in a dose-dependent fashion, and the effects were reversed by IGF-I. Anti-IGF-I antibody mimicked the inhibitory effects of IGFBP-4 and -5. Forskolin, cholera toxin, and 8-bromo-cAMP increased Inh-alpha production approximately 3.5-fold, and the effects were blocked by IGFBP-4 or -5. Increases in Inh-alpha by FSH, IGF-I, forskolin, cholera toxin, and 8-bromo-cAMP were totally blocked by the protein tyrosine kinase inhibitor, tyrphostin A23. In summary, these results suggest that the stimulation of Inh-alpha expression by FSH requires activation of protein tyrosine kinases by endogenously produced IGF-I. We propose that the IGF-I signaling is obligatory for FSH stimulation of Inh-alpha expression in rat GC.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Factor I del Crecimiento Similar a la Insulina
/
Expresión Génica
/
Tirfostinos
/
Hormona Folículo Estimulante
/
Células de la Granulosa
/
Inhibinas
Límite:
Animals
Idioma:
En
Revista:
Biol Reprod
Año:
1998
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos