Does galanin inhibit insulin secretion by opening of the ATP-regulated K+ channel in the beta-cell?
The intrapancreatic neuropeptide galanin potently inhibits glucose-induced insulin secretion. This effect is in part due to a repolarization of the beta-cells and ensuring reduction in the cytoplasmic free Ca2+ concentration, [Ca2+]i. We propos that galanin inhibition of beta-cell action potentials is associated with the appearance of ATP-regulated K+ channels. Galanin opens K+ channels in a patch membrane when applied to the external solution in the cell-attached patch configuration. However, galanin does not detectably increase K+ permeability during whole-cell experiments, even when GTP was included in the internal solution. Our findings are not consistent with a direct effect of galanin on the K+ channels, but rather indicate that the effect of the neuropeptide is mediated by some intracellular coupling factor(s).
Ahrén
B
B
Department of Surgery, Lund University, Sweden.
Berggren
P O
PO
Bokvist
K
K
Rorsman
P
P
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D019004:Galanin; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D009479:Neuropeptides / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*
D007328:Insulin; D009479:Neuropeptides; D010455:Peptides; D015221:Potassium Channels; D019004:Galanin; D000255:Adenosine Triphosphate; D002118:Calcium