Influencing the between-feeding and endocrine responses of plasma ghrelin in healthy dogs.
OBJECTIVE
Ghrelin has recently been isolated from rat and human stomach as an endogenous ligand for the growth hormone (GH) secretagog receptor. Using beagle dogs, we investigated the distribution of ghrelin in the stomach and its possible role.


METHODS
We examined: (i) GH release in response to ghrelin injection (0.5 or 5 microg/kg, i.v.), (ii) gastric localization of ghrelin-immunostained cells, (iii) changes in daily food consumption after ghrelin injection (3, 10, and 20 microg/kg, i.v.), (iv) plasma ghrelin levels under regular, but restricted feeding conditions, and (v) variations in plasma ghrelin levels in relatively lean, normal and obese dogs.


RESULTS
Administration of ghrelin to dogs promptly increased circulating GH concentrations, although this effect was transitory and was maintained for only 20 min. Ghrelin was localized in the stomach fundus and body, but none was detected in either the pylorus or cardia. Administration of ghrelin at a dose of 20 microg/kg increased the daily food intake of beagle dogs. Plasma ghrelin levels peaked just before meal times, and then returned to basal levels. Obese dogs had higher plasma ghrelin levels than did normal and lean dogs.


CONCLUSIONS
These results indicate that ghrelin is a potent GH secretagog in dogs. The distribution of ghrelin-immunoreactive cells in the canine stomach resembles that of both the murine and human stomach. Ghrelin participates in the control of feeding behavior and energy homeostasis in dogs and may, therefore, be involved in the development of obesity.
Yokoyama
Masayuki
M
Department of Veterinary Physiology, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2155, Japan.
Nakahara
Keiko
K
Kojima
Masayasu
M
Hosoda
Hiroshi
H
Kangawa
Kenji
K
Murakami
Noboru
N
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004285:Dogs / Q000097:blood / Q000378:metabolism*; D004435:Eating / Q000502:physiology; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism*; D054439:Ghrelin; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D009765:Obesity / Q000097:blood / Q000378:metabolism; D036361:Peptide Hormones / Q000097:blood* / Q000378:metabolism / Q000494:pharmacology*; D011897:Random Allocation; D013997:Time Factors
D054439:Ghrelin; D036361:Peptide Hormones; D013006:Growth Hormone