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  • Title: NPPB block of the intermediate-conductance Ca2+-activated K+ channel.
    Author: Fioretti B, Castigli E, Calzuola I, Harper AA, Franciolini F, Catacuzzeno L.
    Journal: Eur J Pharmacol; 2004 Aug 16; 497(1):1-6. PubMed ID: 15321728.
    Abstract:
    We have shown that the Cl(-) channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) also blocks the intermediate-conductance Ca(2+)-activated K(+) (IK(Ca)) current in human leukemic HL-60 and glioblastoma GL-15 cell lines. The macroscopic IK(Ca) current was activated by ionomycin plus 1-EBIO, and identified as intermediate conductance by being fully blocked by charybdotoxin, clotrimazole, nitrendipine (L-type Ca(2+) channel blocker), and NS1619 (BK(Ca) channel opener), but not by D-tubocurarine or TEA. The IK(Ca) current was blocked by NPPB in a reversible dose-dependent manner, with an IC(50) of 39 microM in HL-60 and 125 microM in GL-15 cells. The block of the IK(Ca) current was also recorded at the single channel level in excised inside-out patches. As expected, NPPB also blocked the volume-activated Cl(-) current expressed by GL-15 cells, with an IC(50) of 44 microM. The functional implications of IK(Ca) current block by NPPB are discussed.
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