Influence of quinidine on diclofenac metabolism versus influence of diclofenac on quinidine metabolism in incubations with recombinant CYP3A43-a
| Formation of 5-Hydroxydiclofenac3-b | Formation of 3-Hydroxyquinidine3-b | ||||
|---|---|---|---|---|---|
| Quinidine | Km | Vmax | Diclofenac | Km | Vmax |
| μM | nmol/min/nmol | μM | nmol/min/nmol | ||
| 0 | 71.1 ± 25.6 | 13.2 ± 1.7 | 0 | 1.3 ± 0.3 | 5.1 ± 0.3 |
| 0.5 | 55.9 ± 17.2 | 19.2 ± 2.1 | 30 | 1.3 ± 0.1 | 5.1 ± 0.1 |
| 1 | 56.6 ± 12.7 | 32.9 ± 2.4 | 50 | 1.2 ± 0.1 | 5.9 ± 0.2 |
| 2.5 | 68.6 ± 11.5 | 44.4 ± 4.9 | 70 | 1.0 ± 0.2 | 5.8 ± 0.2 |
| 5 | 54.2 ± 14.7 | 53.6 ± 4.6 | 80 | 1.3 ± 0.1 | 6.0 ± 0.1 |
| 7.5 | 55.9 ± 12.4 | 55.6 ± 3.9 | 90 | 1.5 ± 0.3 | 7.6 ± 0.3 |
| 10 | 63.5 ± 13.5 | 56.5 ± 4.1 | 100 | 2.6 ± 0.6 | 6.2 ± 0.4 |
| 20 | 43.9 ± 10.6 | 55.0 ± 3.7 | 110 | 1.9 ± 0.6 | 4.7 ± 0.4 |
| 30 | 55.4 ± 10.0 | 57.6 ± 3.3 | 120 | 2.7 ± 0.4 | 4.9 ± 0.2 |
| 150 | 2.3 ± 0.6 | 3.8 ± 0.3 | |||
| 200 | 2.2 ± 0.6 | 3.6 ± 0.2 | |||
| 300 | 1.1 ± 0.1 | 3.6 ± 0.1 | |||
↵3-a Diclofenac and glutathione in phosphate buffer (pH 7.4) and quinidine in methanol were added to recombinant CYP3A4+OR+b5 suspended in phosphate buffer (0.1 M, pH 7.4) containing EDTA. Controls contained no quinidine but the same amount of methanol, or contained no diclofenac but same amount of phosphate buffer. Incubations were performed in duplicate.
↵3-b The kinetic parameters were determined based on the Michaelis-Menten equation. Data are presented as mean ± S.E.