Growth hormone (GH)-releasing hormone secretion is stimulated by a new GH-releasing hexapeptide in sheep.
The acute effect of a new GH-releasing peptide, hexarelin (1 mg, iv), on GH secretion and the mechanisms involved in its changes were investigated in conscious sheep. Peripheral GH levels and GH-releasing hormone (GHRH) and somatostatin concentrations in hypophysial portal blood were measured in six rams. An increase in jugular GH levels was observed 15 min after hexarelin injection (9.1 +/- 1.8 vs. 3.9 +/- 0.8 ng/ml; P < 0.05). This was associated with a stimulation of GHRH release into hypophysial portal blood (145.4 +/- 19.9 vs. 59.2 +/- 10.8 pg/ml; P < 0.01) without a change in somatostatin secretion. Our data indicate that GH-releasing peptide-induced GH stimulation in the sheep involves an activation of GHRH neurons in addition to the previously demonstrated direct effect on the pituitary cells.
Guillaume
V
V
Laboratoire de Neuroendocrinologie Expérimentale, Institut Fédératif Jean Roche, INSERM U-297, Faculté de Médecine Nord, Marseille, France.
Magnan
E
E
Cataldi
M
M
Dutour
A
A
Sauze
N
N
Renard
M
M
Razafindraibe
H
H
Conte-Devolx
B
B
Deghenghi
R
R
Lenaerts
V
V
D000818:Animals; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000097:blood / Q000378:metabolism*; D006133:Growth Substances / Q000494:pharmacology; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000098:blood supply; D011168:Portal System; D012756:Sheep; D013004:Somatostatin / Q000097:blood
D006133:Growth Substances; D009842:Oligopeptides; C086184:hexarelin; D013004:Somatostatin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone