title: Size-related and size-unrelated functional heterogeneity among pancreatic islets.
abstract: Functional heterogeneity of pancreatic islets was systematically analyzed for the first time using freshly isolated single rat pancreatic islets. First, 60 islets were sequentially exposed to 3, 9.4, 15.6, and 24.1 mM glucose for 30 min each in incubation experiments: 36 (60%) responded in a concentration-dependent and 19 (32%) in an all-or-none manner, and 5 (8%) islets did not respond to high glucose. As a group, the larger the islet, the higher the beta cell glucose sensitivity. However, glucose-stimulated elevation of [Ca2+]i in the beta cell. insulin/glucagon ratio in the islet, and expression of glucose transporter 2, glucokinase, and pancreatic duodenal homeobox factor-1 in the beta cell were not significantly related to islet size. Second, 50 islets were stimulated with 16.7 mM glucose in perifusion. A biphasic insulin release was found in 39 (78%), and no or little first phase response in 11 (22%) islets, irrespective of the islet size. Nevertheless, when the response was plotted as a group, it was clearly biphasic. Islet size, insulin content and the amount of insulin release were positively correlated with each other. In conclusion, there are size-related and size-unrelated functional diversity among pancreatic islets. The reason for such heterogeneity remained to be determined.
authors.affiliation: Department of Aging Medicine and Geriatrics, Shinshu University School of Medicine, Matsumoto, Japan. traizawa@hsp.md.shinshu-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Aizawa
authors.forename: T
authors.initials: T
authors.lastname: Kaneko
authors.forename: K
authors.initials: K
authors.lastname: Yamauchi
authors.forename: H
authors.initials: H
authors.lastname: Yajima
authors.forename: T
authors.initials: T
authors.lastname: Nishizawa
authors.forename: T
authors.initials: T
authors.lastname: Yada
authors.forename: H
authors.initials: H
authors.lastname: Matsukawa
authors.forename: M
authors.initials: M
authors.lastname: Nagai
authors.forename: S
authors.initials: S
authors.lastname: Yamada
authors.forename: Y
authors.initials: Y
authors.lastname: Sato
authors.forename: M
authors.initials: M
authors.lastname: Komatsu
authors.forename: N
authors.initials: N
authors.lastname: Itoh
authors.forename: H
authors.initials: H
authors.lastname: Hidaka
authors.forename: Y
authors.initials: Y
authors.lastname: Kajimoto
authors.forename: K
authors.initials: K
authors.lastname: Hashizume
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism; D005941:Glucokinase / Q000096:biosynthesis; D051273:Glucose Transporter Type 2; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar
chemical_list: D051273:Glucose Transporter Type 2; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D005934:Glucagon; D005941:Glucokinase; D002118:Calcium