Sulfonylurea affinities of SUR isoforms in membranes or intact cells transiently expressed with or without inward rectifier subunit
| Radioligand | Glibenclamide | Glipizide | Meglitinide | Tolbutamide | |
|---|---|---|---|---|---|
| ha SUR1 | glib. | 0.72 ± 0.06 nM (0.94) | 17 ± 3 nM (0.94) | 6.9 ± 0.6 μM (0.93) | 29 ± 2 μM (0.98) |
| ha SUR1, IS | glib. | 0.85 ± 0.03 nM (0.98) | 22 ± 4 nM (0.96) | 6.4 ± 0.3 μM (1.02) | 33 ± 4 μM (0.93) |
| ha SUR1/KIR6.2 | glib. | 0.78 ± 0.07 nM (1.03) | 16 ± 2 nM (0.93) | n.d. | 25 ± 3 μM (1.04) |
| ha SUR1∼KIR6.2 | glib. | 0.83 ± 0.07 nM (0.97) | 20 ± 3 nM (1.02) | n.d. | 37 ± 2 μM (0.96) |
| ha SUR1, cells | glib. | 0.62 ± 0.04 nM (0.96) | 15 ± 5 nM (1.00) | 6.3 ± 0.3 μM (0.99) | 26 ± 3 μM (1.05) |
| ha SUR1/KIR6.2, cells | glib. | 0.75 ± 0.08 nM (1.01) | 14 ± 2 nM (0.98) | n.d. | 31 ± 1 μM (0.93) |
| ha SUR1 1540X | glib. | 0.65 ± 0.04 nM (0.97) | 19 ± 2 nM (0.92) | n.d. | 27 ± 2 μM (0.94) |
| hu SUR1 | glib. | 0.55 ± 0.09 nM (0.94) | 13 ± 4 nM (0.94) | 7.0 ± 1 μM (0.93) | 22 ± 2 μM (0.98) |
| rat SUR2B | P1075 | 0.25 ± 0.03 μM (0.99) | 6.1 ± 0.3 μM (0.99) | 9.2 ± 1.3 μM (0.93) | 260 ± 10 μM (1.02) |
| rat SUR2B, IS | P1075 | 0.30 ± 0.06 μM (1.04) | 5.6 ± 0.2 μM (0.95) | n.d. | 240 ± 14 μM (0.94) |
| rat SUR2B/KIR6.2 | P1075 | 0.29 ± 0.05 μM (0.93) | 6.3 ± 0.5 μM (0.92) | n.d. | 290 ± 10 μM (0.99) |
| rat SUR2B, cells | P1075 | 0.32 ± 0.03 μM (0.97) | 7.1 ± 0.6 μM (0.98) | 7.8 ± 0.7 μM (1.00) | 300 ± 12 μM (1.03) |
| rat SUR2B, cells | glib. | 0.35 ± 0.09 μM (1.02) | 5.8 ± 0.8 μM (1.02) | n.d. | 280 ± 15 μM (1.00) |
| rat SUR2B/KIR6.1, cells | P1075 | 0.38 ± 0.07 μM (1.04) | 6.4 ± 0.2 μM (0.98) | n.d. | 270 ± 12 μM (0.94) |
| rat SUR2B/KIR6.2, cells | P1075 | 0.37 ± 0.06 μM (1.01) | 5.5 ± 0.4 μM (0.96) | n.d. | 250 ± 10 μM (0.98) |
| hu SUR2B | P1075 | 0.27 ± 0.04 μM (0.96) | 8.0 ± 0.4 μM (0.90) | 8.2 ± 0.8 μM (0.94) | 310 ± 18 μM (1.06) |
| rat SUR2A | P1075 | 0.29 ± 0.04 μM (1.01) | 5.3 ± 0.2 μM (1.00) | 6.9 ± 0.2 μM (0.93) | 230 ± 16 μM (1.05) |
| rat SUR2A, cells | P1075 | 0.31 ± 0.08 μM (1.02) | 7.1 ± 0.5 μM (1.04) | n.d. | 290 ± 19 μM (1.02) |
| rat SUR2A/KIR6.2, cells | P1075 | 0.26 ± 0.05 μM (0.97) | 5.9 ± 0.3 μM (0.96) | n.d. | 280 ± 14 μM (0.95) |
| SUR2/ct1 | P1075 | 0.23 ± 0.04 μM (0.96) | 5.0 ± 0.1 μM (1.03) | 7.2 ± 0.4 μM (1.01) | 250 ± 16 μM (1.06) |
Dissociation constants (K Ds) for glibenclamide, glipizide, meglitinide, or tolbutamide were assessed by displacement of [3H]glibenclamide (glib.) or [3H]P1075 (P1075) as detailed in Experimental Procedures. Hill coefficients are given in brackets. Results shown as mean (± S.E.M. for K D values) from three to five independent displacement curves. SUR isoforms were transiently expressed in COS-7 cells either alone (e.g. ha SUR1) or in combination with KIR6.1 or KIR6.2 (e.g., ha SUR1/KIR6.2). Assays were performed using a membrane fraction of these cells (e.g., ha SUR1) or intact cells (e.g., ha SUR1, cells). “IS” indicates use of intracellular solution instead of Tris-buffer as incubation medium (see Experimental Procedures); ha SUR1 ∼ KIR6.2 is a fusion of hamster SUR1 and rat KIR6.2, ha SUR1 1540X a mutation lacking the C-terminal 42 aminoacids and SUR2/ct1 a chimera consisting of rat SUR2A with the C terminus of hamster SUR1 (seeExperimental Procedures); ha = hamster, hu = human, n.d. = not determined.