Inhibition of methimazole S-oxidation in dog microsomes by FMO substrates
| Microsomes | Addition | Methimazole S-Oxidase Activity | |
|---|---|---|---|
| nmol/min/mg | % of inhibition | ||
| Liver | Control | 6.2 ± 0.3 | 0 |
| + Imipramine (0.7 mM) | 1.7 ± 0.4 | 73 | |
| + Trimethylamine (1 mM) | 5.5 ± 0.5 | 11 | |
| Lung | Control | 3.4 ± 0.3 | 0 |
| + Imipramine (0.7 mM) | 2.9 ± 0.1 | 35 | |
| + Trimethylamine (1 mM) | 2.2 ± 0.2 | 16 | |
| Kidney | Control | N.D. | N.D. |
| +Imipramine (0.7 mM) | — | — | |
| + Trimethylamine (1 mM) | — | — | |
Each value represents the mean ± S.D. of four determinations. The rate of methimazole S-oxidation was monitored for 2 min at 37°C; then the substrates were added to the sample and reference cuvettes, and the reaction rate was recorded for 3 min.
N.D. not detected; —, not determined.