Bradykinin enhances membrane electrical activity of pancreatic beta cells in the presence of low glucose concentrations.
In most of cells bradykinin (BK) induces intracellular calcium mobilization. In pancreatic beta cells intracellular calcium is a major signal for insulin secretion. In these cells, glucose metabolism yields intracellular ATP which blocks membrane potassium channels. The membrane depolarizes, voltage-dependent Ca2+ channels are activated and the intracellular calcium load allows insulin secretion. Repolarization occurs due to activation of the Ca2+-dependent K+ channel. The insulin secretion depends on the integrity of this oscillatory process (bursts). Therefore, we decided to determine whether BK (100 nM) induces bursts in the presence of a non-stimulatory glucose concentration (5.6 mM). During continuous membrane voltage recording, our results showed that bursts were obtained with 11 mM glucose, blocked with 5.6 mM glucose and recovered with 5.6 mM glucose plus 100 nM BK. Thus, the stimulatory process obtained in the presence of BK and of a non-stimulatory concentration of glucose in the present study suggests that BK may facilitate the action of glucose on beta cell secretion.
Moura
A S
AS
Laboratório de Fisiologia Celular, Departamento de Fisiologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil. asmoura@uerj.br
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D004594:Electrophysiology; D005947:Glucose / Q000032:analysis / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D015221:Potassium Channels / Q000378:metabolism
D007328:Insulin; D015221:Potassium Channels; D005947:Glucose; D001920:Bradykinin