Substance P stimulates Growth Hormone (GH) and GH-Releasing Hormone (GHRH) secretions through tachykinin NK2 receptors in sheep |
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Authors: | Lemamy Guy-Joseph Guillaume Viviane Ndéboko Bénédicte Mouecoucou Justine Oliver Charles |
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Affiliation: | University of Aix-Marseille and Institut National de la Santé Et de la Recherche Médicale (INSERM) U 297, Laboratory of Experimental Neuroendocrinology, Boulevard P. Dramard, 13916 Marseille cedex 20, France. guylemamy@yahoo.fr |
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Abstract: | Substance P is ubiquitous undecapeptide belonging to the tachykinins family. It has been found in the hypothalamus and is involved in the hypothalamo-hypophysial axis in several mammals, including human. Previous studies have shown that substance P increases GH secretions in rats and human. In this study, we have shown that intravenously infused substance P in sheep caused an increased level of Growth Hormone (GH) and GH-Releasing Hormone (GHRH), and decreased Somatotropin Release Inhibiting Hormone (SRIH) secretions. GH was obtained from peripheral blood. GHRH and SRIH were directly collected from hypophysial portal blood, using a trans-nasal surgery technique in a vigil sheep that allowed accessing to hypothalamo-hypophysial portal vessels. Hormones assays were performed by radioimmunoassay (RIA). Moreover, we showed that substance P-induced GH and GHRH secretion appears to be mediated by NK2 tachykinin receptors, since it is specifically blocked by a non peptidic tachykinin NK2 receptor antagonist (SR48968, Sanofi, Montpellier, France) whereas a non peptidic tachykinin NK1 antagonist (SR140333, Sanofi, Montpellier, France) failed to modify GH and GHRH hormones secretions. |
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Keywords: | Substance P GH GHRH SRIH NK2 receptor |
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