Lack of gonadotropin releasing-hormone action on in vivo and in vitro growth hormone release,in rainbow trout (Oncorhynchus mykiss) |
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| Institution: | 1. Neuroscience Program, Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N Mathews Ave, Urbana, IL, USA;2. Department of Biological Sciences, David Clark Labs, 100 Brooks Avenue, North Carolina State University, Raleigh, NC, USA;1. Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA;2. Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA;3. Department of Medicine, Division of Hematology and Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA;4. School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA;5. Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, AL, 35233, USA;1. MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary;2. Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary;3. Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary;1. UMR-Intrepid, CIRAD, Montpellier, France;2. Institute of Anatomy, University of Zurich, Switzerland;3. Université Polytechnique de Bobo-Dioulasso, Burkina Faso;4. INRA, UR1037 LPGP Fish Physiology and Genomics, F-35000 Rennes, France |
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| Abstract: | In order to understand the mechanisms implicated at the hypothalamo-pituitary level in growth-reproduction interaction in salmonids, the gonadotropin-releasing hormone (GnRH) action on growth hormone (GH) release was studied, in rainbow trout (Oncorhynchus mykiss). In vivo, acute treatment with salmon GnRH (sGnRH), chicken GnRH-II (cGnRH-II) and an sGnRH analogue (DArg6Pro9)sGnRH] was performed on catheterized fish. The different forms of GnRH have no effect on plasma GH levels of immature and mature fish, but induce a stimulation of gonadotropin (GtH) release in mature fish. In the present work we have adapted and validated a culture system for GH regulation studies. In this system, increasing doses of sGnRH, (DArg6Pro9)sGnRH and cGnRH-II are inactive on GH release (24 hr incubation) in immature or mature fish, but stimulate GtH release in a dose-dependent manner. sGnRH (10?6 M) has no action on GH release, whatever the incubation time (15 min–24 hr). In a perifusion system, sGnRH also has no action on GH release but stimulates GtH release. The present results obtained using in vivo and in vitro techniques adapted for GH regulation studies, show that GnRH does not function as a growth hormone-releasing factor in rainbow trout as it does in goldfish. |
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