Puberty in teleosts: new insights into the role of peripheral signals in the stimulation of pituitary gonadotropins
Dufour, S.; Huang, Y.-S.; Rousseau, K.; Sbaihi, M.; Le Belle, N.; Vidal, B.; Marchelidon, J.; Quérat, B.; Burzawa-Gérard, E.; Chang, C.-F.; Schmitz, M. (2000). Puberty in teleosts: new insights into the role of peripheral signals in the stimulation of pituitary gonadotropins, in: Norberg, B. et al. Proceedings of the 6th International Symposium on the Reproductive Physiology of Fish, Bergen, Norway, July 4-9, 1999. pp. 455-461
In: Norberg, B. et al. (2000). Proceedings of the 6th International Symposium on the Reproductive Physiology of Fish, Bergen, Norway, July 4-9, 1999. International Symposium on the Reproductive Physiology of Fish, 6. Department of Fisheries and Marine Biology, University of Bergen: Bergen. ISBN 82-7461-048-2. 499 pp., more
In: International Symposium on the Reproductive Physiology of Fish. Museo Nacional de Ciencias Naturales. , more
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Document type: Conference paper
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| Authors | | Top |
- Dufour, S.
- Huang, Y.-S.
- Rousseau, K.
- Sbaihi, M.
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- Le Belle, N.
- Vidal, B.
- Marchelidon, J.
- Quérat, B.
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- Burzawa-Gérard, E.
- Chang, C.-F.
- Schmitz, M.
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| Abstract |
In fish, as in other vertebrates, the first sexual maturation ("puberty") is characterized by an activation of the brain-pituitary-gonadal axis. Regulatory mechanisms underlying this activation are still poorly understood. This paper focuses on the role of peripheral signals in pubertal stimulation of pituitary gonadotropins in teleosts, with special reference to the European eel. Studies on the ontogeny of gonadotropins (GtH1 = FSH; GtH2 = LH) reveal differences among teleosts in the pubertal profiles of FSH and LH. This suggests species-related variations in the regulation of FSH and LH, and in their respective roles in the initiation of puberty and control of gametogenesis. Sexual steroids exert a positive feedback on LH in juvenile teleosts, but variations in steroid specificity and mechanisms of action occur between teleost species. A few data on steroid feedback on FSH in juvenile teleosts suggest species-related variations, with positive, negative or no effects. The steroid positive feedback on LH can play a specific role in teleosts as an amplifier during pubertal process. Field and aquaculture data show that age at puberty is strongly related to body growth rate and metabolic status, in teleosts as in other vertebrates. We investigated the potential roles of growth and metabolic hormones in the stimulation of eel LH production. Insulin-like growth factor (IGF 1), produced by the liver under the control of growth hormone, and involved in the control of body growth, had a stimulatory effect on eel LH synthesis and release, exerted directly at the pituitary cell level. Preliminary data indicate that metabolic hormones involved in the control of accumulation of energy stores, such as insulin and leptin, may also be able to stimulate eel LH production. Cortisol, an adrenal hormone involved in the mobilization of energy stores necessary for gonadal growth and reproductive migration, also stimulated eel LH, by a direct pituitary action. In contrast, no effect of other metabolic hormones, such as thyroid hormones, T3 and T4, was observed. These data demonstrate that teleost gonadotropic cells are a key-site of integration of various peripheral growth and metabolic cues involved in the triggering of puberty. Peripheral signals concerning body growth (IGF 1) and accumulation of energy stores (insulin, leptin) are likely to act as early triggering signals for determining the onset of puberty, while energy mobilization signal (cortisol) and sex steroid positive feedback may participate in further progress of puberty. |
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