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Barium(2+) inhibits KCNQ1. 9 / 9
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"Like with many K + channels, Ba 2+ block of KCNQ1 currents was voltage dependent, with weaker inhibition at depolarized potentials (XREF_FIG B and 11 B)."
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"When measured upon a 3-s test potential at +30 mV and from a -60-mV tail potential, 10 mM Ba 2+ reduced by ~ 61% the fractional inactivation of KCNQ1 from 0.54 +/- 0.07 to 0.21 +/- 0.03 (n = 7) with an EC 50 = 0.94 +/- 0.07 mM (XREF_FIG C)."
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"For example, 10 mM Ba 2+ blocked at -20 mV the KCNQ1 K + currents with fast and slow time constants tau f = 220 +/- 43 ms and tau s = 1,073 +/- 128 ms, respectively (n = 8) (XREF_FIG B)."
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"Under these conditions, the KCNQ1 current was blocked by 51 +/- 7% (n = 6) at the beginning of the depolarizing step (at 200 ms) and by 31 +/- 3% (n = 6) at the end of the pulse (at 2,000 ms), thus providing strong evidence that barium could block KCNQ1 channels in the closed state."
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"For example, at +30 mV 10 mM Ba 2+ led to a 54 +/- 2% block of KCNQ1 outward currents in 50 mM [K +] 0, compared with a 72 +/- 3% inhibition in 2 mM [K +] 0 (P < 0.01, n = 10; XREF_FIG and XREF_FIG)."
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"Barium produced a marked slowing of KCNQ1 activation kinetics that is well seen at all potentials (XREF_FIG A and 6)."
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"In low external K + (2 mM), extracellular Ba 2+ produced a time dependent inhibition of homomeric KCNQ1 K + currents when expressed in Xenopus oocytes."
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"The delta value obtained for the deep slow site of Ba 2+ block of KCNQ1 is similar to that found for Shaker K + channels (delta = 0.35), but is lower than that obtained for the high affinity Ba 2+ block of the inward-rectifier Kir2.1 channels (delta = 0.62) or that found for the two-pore domain K + channel KCNK0 (delta = 0.60)."
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"Barium also blocked KCNQ1 channels in the closed state."
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