Activation of Ca(2+)-dependent K(+) channels contributes to rhythmic firing of action potentials in mouse pancreatic beta cells.
We have applied the perforated patch whole-cell technique to beta cells within intact pancreatic islets to identify the current underlying the glucose-induced rhythmic firing of action potentials. Trains of depolarizations (to simulate glucose-induced electrical activity) resulted in the gradual (time constant: 2.3 s) development of a small (<0.8 nS) K(+) conductance. The current was dependent on Ca(2+) influx but unaffected by apamin and charybdotoxin, two blockers of Ca(2+)-activated K(+) channels, and was insensitive to tolbutamide (a blocker of ATP-regulated K(+) channels) but partially (>60%) blocked by high (10-20 mM) concentrations of tetraethylammonium. Upon cessation of electrical stimulation, the current deactivated exponentially with a time constant of 6.5 s. This is similar to the interval between two successive bursts of action potentials. We propose that this Ca(2+)-activated K(+) current plays an important role in the generation of oscillatory electrical activity in the beta cell.
Göpel
S O
SO
Department of Physiological Sciences, Division of Molecular and Cellular Physiology, Lund University, SE-223 62 Lund, Sweden.
Kanno
T
T
Barg
S
S
Eliasson
L
L
Galvanovskis
J
J
Renström
E
E
Rorsman
P
P
D018528:ATP-Binding Cassette Transporters; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004594:Electrophysiology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000502:physiology*; D054086:KATP Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000819:agonists / Q000378:metabolism / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D024661:Potassium Channels, Inwardly Rectifying; D014044:Tolbutamide / Q000494:pharmacology
D018528:ATP-Binding Cassette Transporters; D007004:Hypoglycemic Agents; D054086:KATP Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024661:Potassium Channels, Inwardly Rectifying; C092520:uK-ATP-1 potassium channel; D014044:Tolbutamide