Incubation | K_{i} (μM) | |
---|---|---|
Total^{4-a} | Unbound^{4-b} | |
Without Hsa and Hlc | 6 | 6 |
With Hlc | 8 | 8 |
With Hsa | 20 (40)^{4-c} | 4 |
With Hsa and Hlc | 36 (72)^{4-c} | 9 |
All incubations were performed in duplicate; the mean of duplicate determinations was used for the nonlinear regression analysis to estimate the K_{i} values (see Experimental Procedures for details).
↵4-a Total K_{i}of gemfibrozil estimated using the competitive inhibition model:V_{i} = V_{max} · S_{u}/[K_{m} (1 + I/K_{i}) + S_{u}], where S_{u} is the unbound tolbutamide concentration, and I is the total gemfibrozil concentration.
↵4-b Unbound K_{i} of gemfibrozil estimated using V_{i} =V_{max} · S_{u}/[K_{m}(1 + I_{u}/K_{i}) + S_{u}], where S_{u} is unbound tolbutamide, and I_{u} is unbound gemfibrozil.
↵4-c Total K_{i} of gemfibrozil estimated using V_{i} =V_{max} · S/[K_{m} (1 + I/K_{i}) + S], where S is total tolbutamide, and I is total gemfibrozil.