Glucagon-like peptide 1 (7-36) amide stimulates exocytosis in human pancreatic beta-cells by both proximal and distal regulatory steps in stimulus-secretion coupling
Research output: Contribution to journal › Journal article › Research › peer-review
The effect of glucagon-like peptide 1(7-36) amide [GLP-1(7-36) amide] on membrane potential, whole-cell ATP-sensitive potassium channel (K[ATP]) and Ca2+ currents, cytoplasmic Ca2+ concentration, and exocytosis was explored in single human beta-cells. GLP-1(7-36) amide induced membrane depolarization that was associated with inhibition of whole-cell K(ATP) current. In addition, GLP-1(7-36) amide (and forskolin) produced greater than fourfold potentiation of Ca2+-dependent exocytosis. The latter effect resulted in part (40%) from acceleration of Ca2+ influx through voltage-dependent (L-type) Ca2+ channels. More importantly, GLP-1(7-36) amide (via generation of cyclic AMP and activation of protein kinase A) potentiated exocytosis at a site distal to a rise in the cytoplasmic Ca2+ concentration. Photorelease of caged cAMP produced a two- to threefold potentiation of exocytosis when the cytoplasmic Ca2+ concentrations were clamped at > or =170 nmol/l. The effect of GLP-1(7-36) amide was antagonized by the islet hormone somatostatin. Similar effects on membrane potential, ion conductances, and exocytosis were observed with glucose-dependent insulinotropic polypeptide (GIP), the second major incretin. The present data suggest that the strong insulinotropic action of GLP-1(7-36) amide and GIP in humans results from its interaction with several proximal as well as distal important regulatory steps in the stimulus-secretion coupling.
|Number of pages||9|
|Publication status||Published - 1998|
- Adult, Calcium, Calcium Channels, Cells, Cultured, Cyclic AMP, Cyclic AMP-Dependent Protein Kinases, Exocytosis, Female, Forskolin, Gastric Inhibitory Polypeptide, Glucagon, Glucagon-Like Peptide 1, Glucagon-Like Peptides, Humans, Islets of Langerhans, Male, Membrane Potentials, Middle Aged, Neurotransmitter Agents, Peptide Fragments, Potassium Channels, Somatostatin