title: Insulin-like growth factor-I stimulates gonadotrophin production from eel pituitary cells: a possible metabolic signal for induction of puberty.
abstract: Insulin-like growth factor (IGF)-I has been suggested as a potential signal linking growth and puberty in mammals. Using the juvenile European eel as a model, we employed a long-term, serum-free primary culture of pituitary cells to study the direct effect of IGF-I on gonadotrophin (GtH-II=LH) production. IGF-I increased both cell content and release of GtH-II in a time- and dose-dependent manner. IGF-I and IGF-II had similar potencies but insulin was 100-fold less effective, suggesting the implication of an IGF type 1 receptor. Other growth and metabolic factors, such as basic fibroblast growth factor and thyroid hormones, had no effect on GtH-II production. IGF-I did not significantly increase the number of GtH-II immunoreactive cells, indicating that its stimulatory effect on GtH-II production does not result from gonadotroph proliferation. Comparison of IGF-I and somatostatin (SRIH-14) effects showed that both factors inhibited growth hormone (GH) release but only IGF-I stimulated GtH-II production by eel pituitary cells. This indicates that the effect of IGF-I on gonadotrophs is not mediated by the reduction of GH released by somatotrophs into the culture medium. This study demonstrates a specific stimulatory effect of IGF-I on eel GtH-II production, played out directly at the pituitary level. These data obtained in a primitive teleost suggest that the role of IGF-I as a link between body growth and puberty may have been established early in the evolution of vertebrates.
authors.affiliation: Laboratoire de Physiologie Générale et Comparée, Muséum National d'Histoire Naturelle, URA 90 CNRS, 7 rue Cuvier, 75231 Paris Cedex 05, France.
authors.forename: Y S
authors.initials: YS
authors.lastname: Huang
authors.forename: K
authors.initials: K
authors.lastname: Rousseau
authors.forename: N
authors.initials: N
authors.lastname: Le Belle
authors.forename: B
authors.initials: B
authors.lastname: Vidal
authors.forename: E
authors.initials: E
authors.lastname: Burzawa-Gérard
authors.forename: J
authors.initials: J
authors.lastname: Marchelidon
authors.forename: S
authors.initials: S
authors.lastname: Dufour
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004524:Eels / Q000378:metabolism*; D005260:Female; D006065:Gonadotropins, Pituitary / Q000096:biosynthesis*; D013006:Growth Hormone / Q000096:biosynthesis; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012741:Sexual Maturation / Q000502:physiology*; D013268:Stimulation, Chemical; D013997:Time Factors
chemical_list: D006065:Gonadotropins, Pituitary; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone