The GH-releasing effect of ghrelin, a natural GH secretagogue, is only blunted by the infusion of exogenous somatostatin in humans.

Autor: Di Vito, Lidia, Broglio, Fabio, Benso, Andrea, Gottero, Cristina, Prodam, Flavia, Papotti, Mauro, Muccioli, Giampiero, Dieguez, Carlos, Casanueva, Felipe F, Deghenghi, Romano, Ghigo, Ezio, Arvat, Emanuela
Předmět:
Zdroj: Clinical Endocrinology; May2002, Vol. 56 Issue 5, p643-648, 6p
Abstrakt: Summary objective Ghrelin, a 28-amino-acid peptide purified from the stomach and showing a unique structure with an n-octanoyl ester at the serine 3 residue, is a natural ligand of the GH secretagogue (GHS) receptor (GHS-R). Ghrelin strongly stimulates GH secretion in both animals and humans, showing a synergistic effect with GH-releasing hormone (GHRH) but no interaction with synthetic GHS. However, the activity of ghrelin as well as that of non-natural GHS is not fully specific for GH; ghrelin also induces a stimulatory effect on lactotroph and corticotroph secretion, at least in humans. design To further clarify the mechanisms underlying the GH-releasing activity of this natural GHS, we studied the effects of somatostatin (SS, 2·0 µg/kg/h from -30 to +90 min) on the endocrine responses to ghrelin (1·0 µg/kg i.v. at 0 min) in seven normal young male volunteers [age (mean ± SEM) 28·6 ± 2·9 years; body mass index (BMI) 22·1 ± 0·8 kg/m2 ] . In the same subjects, the effect of SS on the GH response to GHRH (1·0 µg/kg i.v. at 0 min) was also studied. measurements Blood samples were taken every 15 min from -30 up to +120 min. GH levels were assayed at each time point in all sessions; PRL, ACTH and cortisol levels were assayed after ghrelin administration alone and during SS infusion. results The GH response to ghrelin (hAUC0′→120′ 2695·0 ± 492·6 µg min/l) was higher (P < 0·01) than that after GHRH (757·1 ± 44·1 µg min/l). SS infusion almost abolished the GH response to GHRH (177·0 ± 37·7 µg min/l, P < 0·01); the GH response to ghrelin was inhibited by SS (993·8 ± 248·5 µg min/l, P < 0·01) but GH levels remained higher (P < 0·05) than with GHRH. Ghrelin induced significant increases in PRL, ACTH and cortisol levels and these responses were not modified by SS.... [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
Externí odkaz: