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Effects of sustained administration of GnRHa on gonadotropin-II (GTH-II) and gonadal steroid levels in adult male sea bass (Dicentrarchus labrax)
Carrillo, M.; Mañanós, E.; Sorbera, L.; Milonas, C.C.; Cuisser, B.; Zohar, J.; Zanuy, S. (2000). Effects of sustained administration of GnRHa on gonadotropin-II (GTH-II) and gonadal steroid levels in adult male sea bass (Dicentrarchus labrax), in: Norberg, B. et al. (Ed.) Proceedings of the 6th International Symposium on the Reproductive Physiology of Fish, Bergen, Norway, July 4-9, 1999. pp. 393-395
In: Norberg, B. et al. (Ed.) (2000). Proceedings of the 6th International Symposium on the Reproductive Physiology of Fish, Bergen, Norway, July 4-9, 1999. 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

Available in  Authors 
    VLIZ: Proceedings [4324]

Keyword
    Marine

Authors  Top 
  • Carrillo, M.
  • Mañanós, E.
  • Sorbera, L.
  • Milonas, C.C.
  • Cuisser, B.
  • Zohar, J.
  • Zanuy, S.

Abstract
    Spermiating European sea bass, were treated either with GnRHa injection in saline (I; 25 µg Kg super(-1) body weight [BW]) or one of three types of controlled-release gonadotropin-releasing hormone agonist (GnRHa)-delivery systems: a fast releasing implant (EVAc; 100 µg Kg super(-1)), a slower-releasing implant (EVSL; 100 µg Kg super(-1)) and biodegradable micro spheres (M; 50 µg Kg super(-1)). Resulting changes in plasma gonadotropin II (GTH-II), Testosterone (T), 11-Ketotestosterone (11-KT) and 17,20 beta -dihydroxy-4-pregnen-3-one (17,20 beta -P) were correlated with changes in milt production previously reported. The GnRHa-delivery systems, M and EVSL, induced a sustained elevation of plasma GTH-II for 35 and 44 days, respectively, while I and M maintained higher GTH-II plasma levels for 2 and 14 days, respectively. Plasma 11-KT levels in treated fish did not differ from those of controls and declined gradually during the experimental period. Plasma T levels of treated fish were also similar to controls remaining elevated during the first 14 days of treatment and declining thereafter except for M and EVSL which exhibited high levels of T for an extra week. Moreover, these were the only two groups with an extended period of spermiation for 35 days. Plasma 17,20 beta -P levels were unchanged after GnRHa treatment except for M and EVSL which showed a significant increase of this progestagen on day 7. In addition, only the EVSL group exhibited another significant peak of 17,20 beta -P on day 28. This study demonstrated that the GnRHa-delivery systems induced a sustained but different elevation of plasma GTH-II levels in sea bass depending on the type of delivery system used, which resulted in a corresponding and long term enhancement of milt production. The possible role of androgens and progestagens is also discussed.

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