Morphological analysis of ghrelin and its receptor distribution in the rat pancreas.
Ghrelin, a novel peptide isolated from stomach tissue of rats and humans, has been identified as the endogenous ligand for the growth hormone secretagogue receptor (GHS-R). In addition to its secretion from the stomach, ghrelin is also expressed in the hypothalamic arcuate nucleus, intestine, kidney, placenta, and pancreas. GHS-R mRNA, on the other hand, is expressed in the hypothalamus, pituitary, heart, lung, liver, pancreas, stomach, intestine, and adipose tissue. Ghrelin is considered to have important roles in feeding regulation and energy metabolism as well as in the release of growth hormone (GH). Recent physiological experiments on the pancreas have shown that ghrelin regulates insulin secretion. However, sites of action of ghrelin in the pancreas are yet to be identified. In this study, to gain insight into the role of ghrelin in rat pancreatic islets, we used immunohistochemistry to determine the localization of ghrelin and GHS-R in islet cells. Double fluorescence immunohistochemistry revealed that weak GHS-R-like immunoreactivity was found in B cells containing insulin. GHS-R immunoreactivity overlapped that of glucagon-like immunoreactive cells. Moreover, both ghrelin and GHS-R-like immunoreactivities were detected mostly in the same cells in the periphery of the islets of Langerhans. These observations suggest that ghrelin is synthesized and secreted from A cells, and acts back on A cells in an autocrine and/or paracrine manner. In addition, ghrelin may act on B cells via GHS-R to regulate insulin secretion.
Kageyama
Haruaki
H
First Department of Anatomy, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Funahashi
Hisayuki
H
Hirayama
Masami
M
Takenoya
Fumiko
F
Kita
Tetsuro
T
Kato
Sachi
S
Sakurai
Junko
J
Lee
Eun Young
EY
Inoue
Shuji
S
Date
Yukari
Y
Nakazato
Masamitsu
M
Kangawa
Kenji
K
Shioda
Seiji
S
D000818:Animals; D054439:Ghrelin; D013006:Growth Hormone / Q000378:metabolism; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D008297:Male; D036361:Peptide Hormones / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000096:biosynthesis*; D054440:Receptors, Ghrelin
D054439:Ghrelin; D007328:Insulin; D036361:Peptide Hormones; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; D013006:Growth Hormone