Ghrelin Is Present in Pancreatic α-Cells of Humans and Rats and Stimulates Insulin Secretion
Author:
Date Yukari12, Nakazato Masamitsu1, Hashiguchi Suzuko34, Dezaki Katsuya3, Mondal Muhtashan S.1, Hosoda Hiroshi2, Kojima Masayasu2, Kangawa Kenji2, Arima Terukatsu4, Matsuo Hisayuki2, Yada Toshihiko3, Matsukura Shigeru1
Affiliation:
1. Department of Internal Medicine, Miyazaki Medical College, Miyazaki, Japan 2. National Cardiovascular Center Research Institute, Osaka, Japan 3. Department of Physiology, Jichi Medical School, Tochigi, Japan 4. Second Department of Internal Medicine, Faculty of Medicine, Kagoshima University, Kagoshima, Japan
Abstract
Ghrelin, a novel growth hormone–releasing peptide isolated from human and rat stomach, is a 28–amino acid peptide with a posttranslational acylation modification that is indispensable for stimulating growth hormone secretion by increasing intracellular Ca2+ concentration. It also functions in the regulation of feeding behavior, energy metabolism, and gastric acid secretion and motility. Using two different antibodies against the NH2- and COOH-terminal regions of ghrelin, we studied its localization in human and rat pancreas by immunohistochemistry. Ghrelin-immunoreactive cells were identified at the periphery of pancreatic islets in both species. Ghrelin co-localized exclusively with glucagon in rat islets, indicating that it is produced in α-cells. We identified ghrelin and des-acyl ghrelin in the rat pancreas using reverse-phase high-performance liquid chromatography combined with two radioimmunoassays. We also detected mRNA encoding ghrelin and its receptor in the rat pancreatic islets. Ghrelin increased the cytosolic free Ca2+ concentration in β-cells and stimulated insulin secretion when it was added to isolated rat pancreatic islets. These findings indicate that ghrelin may regulate islet function in an endocrine and/or paracrine manner.
Publisher
American Diabetes Association
Subject
Endocrinology, Diabetes and Metabolism,Internal Medicine
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