title: Glucagon-like peptide-1 induces a cAMP-dependent increase of [Na+]i associated with insulin secretion in pancreatic beta-cells.
abstract: Glucagon-like peptide-1 (GLP-1) elevates the intracellular free calcium concentration ([Ca2+]i) and insulin secretion in a Na+-dependent manner. To investigate a possible role of Na ion in the action of GLP-1 on pancreatic islet cells, we measured the glucose-and GLP-1-induced intracellular Na+ concentration ([Na+]i), [Ca2+]i, and insulin secretion in hamster islet cells in various concentrations of Na+. The [Na+]i and [Ca2+]i were monitored in islet cells loaded with sodium-binding benzofuran isophthalate and fura 2, respectively. In the presence of 135 mM Na+ and 8 mM glucose, GLP-1 (10 nM) strongly increased the [Na+]i, [Ca2+]i, and insulin secretion. In the presence of 13.5 mM Na+, both glucose and GLP-1 increased neither the [Na+]i nor the [Ca2+]i. In a Na+-free medium, GLP-1 and glucose did not increase the [Na+]i. SQ-22536, an inhibitor of adenylate cyclase, and H-89, an inhibitor of PKA, incompletely inhibited the response. In the presence of both 8 mM glucose and H-89, 8-pCPT-2'-O-Me-cAMP, a PKA-independent cAMP analog, increased the insulin secretion and the [Na+]i. Therefore, we conclude that GLP-1 increases the cAMP level via activation of adenylate cyclase, which augments the membrane Na+ permeability through PKA-dependent and PKA-independent mechanisms, thereby increasing the [Ca2+]i and promoting insulin secretion from hamster islet cells.
authors.affiliation: Department of Hygiene, Dokkyo University School of Medicine, 880 Mibu, Tochigi 321-0293, Japan. y-miura@dokkyomed.ac.jp
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Miura
authors.forename: Hisao
authors.initials: H
authors.lastname: Matsui
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008647:Mesocricetus; D010042:Ouabain / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D011498:Protein Precursors / Q000494:pharmacology*; D012964:Sodium / Q000008:administration & dosage / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology; D013449:Sulfonamides; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; D000067956:Adenylyl Cyclase Inhibitors; D004791:Enzyme Inhibitors; D007328:Insulin; D007546:Isoquinolines; D010446:Peptide Fragments; D011498:Protein Precursors; D013449:Sulfonamides; C017759:9-(tetrahydro-2-furyl)-adenine; D013779:Tetrodotoxin; D013004:Somatostatin; D010042:Ouabain; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D012964:Sodium; D005682:Gadolinium; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D005947:Glucose; D000225:Adenine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium