BAPTA-AM blocks both voltage-gated and Ca2+-activated K+ currents in cultured bovine chromaffin cells.
The effects of the membrane permeant Ca2+ chelator BAPTA-AM on voltage-gated Na+, Ca2+, K+ (I(Na), I(Ca) I(K), respectively) and Ca2+-activated K+ (I(KCa)) currents in cultured bovine chromaffin cells were investigated using the whole-cell patch-clamp technique. Superfusion with BAPTA-AM (50 microM) induced a rapid (< 60 s) and reversible block of both I(KCa) and I(K) (approximately 50%), without affecting either I(Ca) or I(Na). Preincubation with BAPTA-AM (50 microM, 30 min) or cell loading with the nonpermeable active form of BAPTA (10 mM in the pipette solution) permanently blocked I(KCa). BAPTA-AM superfusion (50 microM) also blocked I(K) (approximately 53%) after BAPTA-loading or BAPTA-AM preincubation. In conclusion, we show a fast and reversible block of I(KCa) and I(K) by BAPTA-AM, acting directly on K+ channels before it operates as a Ca2+ chelator, in cultured bovine chromaffin cells.
Urbano
F J
FJ
Laboratorio de Fisiología y Biología Molecular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
Buño
W
W
D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology*; D019439:Chromaffin Cells / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004558:Electric Stimulation; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D015222:Sodium Channels / Q000502:physiology
D015220:Calcium Channels; D002614:Chelating Agents; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D015222:Sodium Channels; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002118:Calcium