Role of BK potassium channels shaping action potentials and the associated [Ca(2+)](i) oscillations in GH(3) rat anterior pituitary cells.
Measurements of electrical activity and intracellular Ca(2+) levels were performed in perforated-patch clamped GH(3) cells to determine the contribution of large-conductance calcium-activated K(+) (BK) channels to action potential repolarization and size of the associated Ca(2+) oscillations. By examining the dependence of action potential (AP) duration on extracellular Ca(2+) levels in the presence and the absence of the specific BK channel blocker paxilline, it is observed that plateau-like action potentials are associated to low densities of paxilline-sensitive currents. Extracellular Ca(2+) increases or paxilline additions are not able to largely modify action potential duration in cells showing a reduced expression of BK currents. Furthermore, specific blockade of these currents with paxilline systematically elongates AP duration, but only under conditions in which short APs and/or prominent BK currents recorded under voltage-clamp mode are present in the same cells. Our data indicate that in GH(3) cells, BK channels act primarily ending the action potential and suggest that by contributing to fine-tuning cellular electrical properties and hence intracellular Ca(2+) variations, BK channels may play an important role on time- and cell-dependent modulation of physiological outputs in adenohypophyseal cells.
Miranda
Pablo
P
Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus del Cristo, Universidad de Oviedo, Oviedo, Spain.
de la Peña
Pilar
P
Gómez-Varela
David
D
Barros
Francisco
F
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism; D015640:Ion Channel Gating / Q000502:physiology; D051036:Large-Conductance Calcium-Activated Potassium Channels; D018408:Patch-Clamp Techniques; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000502:physiology*; D051381:Rats
D007211:Indoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; C048220:paxilline; D002118:Calcium