Kd values of α-ketoisocaproate and related carboxylic acid anions for sulfonylurea receptor binding The listed Kd values (means ± S.E.) and Hill coefficients (means) were obtained from four to six independent competition curves. Kd values were calculated according to Cheng and Prusoff (1973) from the IC50 values of individual binding experiments with membranes from HIT-T15 cells expressing SUR1 (HIT-SUR1) or COS-1 cells transiently expressing hamster SUR1 (SUR1) or rat SUR2B (SUR2B).
| Ligand | HIT-SUR1 | SUR1 | SUR2B | |||
|---|---|---|---|---|---|---|
| Kd | Hill | Kd | Hill | Kd | Hill | |
| mM | mM | mM | ||||
| α-Ketoisovalerate | N.M. | N.M. | 203 ± 11 | –1.12 | 221 ± 21 | –1.11 |
| 3-Methylbutyrate | 253 ± 23 | –1.11 | 279 ± 13 | –1.16 | 207 ± 13 | –1.10 |
| α-Ketovalerate | 98.8 ± 6.4 | –1.02 | 85.9 ± 9.0 | –1.06 | 55.6 ± 1.8 | –1.05 |
| n-Pentanoate | 148 ± 6.5 | –1.07 | 95.3 ± 1.7 | –1.05 | 81.0 ± 1.8 | –1.07 |
| α-Ketoisocaproate | 46.9 ± 1.1 | –1.27 | 57.2 ± 4.0 | –1.11 | 52.9 ± 2.1 | –1.07 |
| 4-Methylpentanoate | 45.6 ± 1.0 | –1.13 | 53.1 ± 0.6 | –1.05 | 25.2 ± 1.0 | –1.05 |
| α-Ketocaproate | 24.9 ± 0.9 | –1.08 | 25.6 ± 0.7 | –1.05 | 21.7 ± 1.8 | –1.09 |
| n-Hexanoate | 42.1 ± 1.1 | –1.04 | 29.7 ± 0.6 | –1.06 | 25.2 ± 0.8 | –1.19 |
| β-Phenylpyruvate | 12.8 ± 0.4 | –1.06 | 15.2 ± 0.3 | –1.10 | 12.7 ± 0.9 | –1.13 |
| 3-Phenylpropionate | 18.5 ± 0.7 | –0.96 | 19.2 ± 0.9 | –1.00 | 13.1 ± 1.0 | –1.11 |
N.M., not measured.