Key result
BAPTA-AM induced a rapid and reversible block of both Ca2+-activated K+ and voltage-gated K+ currents (approximately 50%) in cultured bovine chromaffin cells.
Why the study?
Does BAPTA-AM block voltage-gated and Ca2+-activated K+ currents in cultured bovine chromaffin cells?
Does BAPTA-AM block voltage-gated and Ca2+-activated K+ currents in cultured bovine chromaffin cells?
BAPTA-AM directly blocks voltage-gated and Ca2+-activated K+ channels in bovine chromaffin cells independently of its Ca2+ chelating action.
BAPTA-AM may confound Ca2+ chelation studies via direct K+ blockade; leaves open relevance to human cardiac ion channels.
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.
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Urbano et al. (1998) studied Cultured bovine chromaffin cells. BAPTA-AM was evaluated on Voltage-gated and Ca2+-activated K+ currents. BAPTA-AM induced a rapid and reversible block of both Ca2+-activated K+ and voltage-gated K+ currents (approximately 50%) in cultured bovine chromaffin cells.
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