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Figure 5. Effect of MgADP and MgATP on sulfonylurea inhibition of SUR1- and SUR2A-containing channels. (A–F) Currents in the presence of sulfonylurea (I) expressed as a fraction of that in drug-free solution (Ic). (A and B) Concentration-response relationships for gliclazide inhibition of Kir6.2/SUR1 (A) and Kir6.2/SUR2A-YS (B) channels in the presence and absence (same data as in Fig. 3) of 100 µM MgADP. The lines are the best fit of Eq. 1 to the mean data: IC50 = 72 nM, h = 1.2, a = 0.42 (A, open circles; n = 6); IC50 = 187 nM, h = 1.1, a = 0.07 (A, closed circles; n = 6); IC50 = 1.3 µM, h = 1.1, a = 0.65 (B, open circles; n = 5); IC50 = 1.6 µM, h = 1.2, a = 0.85 (B, closed circles; n = 5). (C and D) Concentration-response relationships for glibenclamide inhibition of Kir6.2/SUR1 (C) and Kir6.2/SUR2A (D) channels in the presence and absence (data from Fig. 3) of 100 µM MgADP. The lines are the best fit of Eq. 1 to the mean data: IC50 = 2.8 nM, h = 0.93, a = 0.32 (C, open circles; n = 6); IC50 = 3.7 nM, h = 1.2, a = 0.04 (C, closed circles; n = 6); IC50 = 13 nM, h = 0.94, a = 0.32 (D, open circles; n = 5); IC50 = 30 nM, h = 0.75, a = 0.68 (D, closed circles; n = 5). (E and F) Concentration-response relationships for gliclazide inhibition of Kir6.2-G334D/SUR1 (E) and Kir6.2-G334D/SUR2A-YS (F) channels in the presence and absence of 1 mM MgATP. The lines are the best fit of Eq. 1 to the mean data: IC50 = 70 nM, h = 1.0, a = 0.39 (E, open squares; n = 6); IC50 = 210 nM, h = 1.0, a = 0.21 (E, closed squares; n = 6); IC50 = 1.3 µM, h = 1.2, a = 0.64 (F, open squares; n = 5); IC50 = 2.5 µM, h = 1.0, a = 0.91 (F, closed squares; n = 5). Mean ± SEM. Image published in: Proks P et al. (2014) © 2014 Proks et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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