Intravenous administration of ghrelin stimulates growth hormone secretion in vagotomized patients as well as normal subjects.
OBJECTIVE
Ghrelin is a potent peptide stimulating GH secretion. Besides its direct action on the pituitary, ghrelin has been reported to stimulate GH release via the vagal afferent nerve in rats. To examine the involvement of vagal nerve in ghrelin-induced GH secretion in humans, GH responses to ghrelin were compared between vagotomized patients with gastrectomy and normal subjects.


METHODS
Ghrelin (0.2 microg/kg) or GHRH (1 microg/kg) was administered intravenously in vagotomized patients and normal subjects on separate days, and plasma GH responses to the stimuli were examined.


RESULTS
Ghrelin caused a significant plasma GH rise in both vagotomized patients and normal subjects. Peak GH levels in vagotomized patients (37.5+/-16.9 ng/ml) were not different from those in normal subjects (29.9+/-23.1 ng/ml). The areas under the curve of GH response to ghrelin did not differ between the two groups. GHRH also increased GH levels, and peak GH levels and areas under the curve after GHRH stimulation were also comparable between vagotomized patients and normal subjects.


CONCLUSIONS
In the present study, the involvement of the afferent vagal nerve in ghrelin-induced GH secretion was not confirmed in humans.
Division of Endocrinology/Metabolism, Neurology and Hematology/Oncology, Department of Clinical Molecular Medicine, Kobe University School of Medicine, Hyogo, 650-0017, Japan.
Ryoko
R
Takeno
Yasuhiko
Y
Okimura
Genzo
G
Iguchi
Masahiko
M
Kishimoto
Takumi
T
Kudo
Kentaro
K
Takahashi
Yutaka
Y
Takahashi
Hidesuke
H
Kaji
Masakazu
M
Ohno
Hajime
H
Ikuta
Yoshikazu
Y
Kuroda
Tetsuji
T
Obara
Hiroshi
H
Hosoda
Kenji
K
Kangawa
Kazuo
K
Chihara
D000328:Adult; D000368:Aged; D005260:Female; D005743:Gastrectomy; D054439:Ghrelin; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage; D019382:Human Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000008:administration & dosage; D036361:Peptide Hormones / Q000008:administration & dosage*; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology / Q000601:surgery
D054439:Ghrelin; D010446:Peptide Fragments; D036361:Peptide Hormones; C036893:somatotropin releasing factor 40; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone