Reaction rates of microsomal testosterone 6β-hydroxylation and erythromycin N-demethylation determined in the presence of both substrates
| Erythromycin (μM) | Testosterone (μM) | Testosterone 6β-Hydroxylation (nmol/min/mg) | Erythromycin N-Demethylation (nmol/min/mg) | ||
|---|---|---|---|---|---|
| Experimental | Calculated | Experimental | Calculated | ||
| 125 | 0 | 0.00 | 0.00 | 1.31 | 1.23 |
| 125 | 50 | 1.55 | 2.61 | 1.04 | 1.07 |
| 125 | 250 | 7.26 | 8.58 | N.D. | 0.78 |
| 250 | 0 | 0.00 | 0.00 | 1.94 | 1.52 |
| 250 | 50 | 1.30 | 1.70 | 1.72 | 1.4 |
| 250 | 250 | 7.53 | 6.34 | 0.42 | 1.12 |
| 500 | 0 | 0.00 | 0.00 | 2.35 | 1.73 |
| 500 | 50 | 1.04 | 1.00 | 2.11 | 1.65 |
| 500 | 250 | 7.04 | 4.17 | 1.09 | 1.44 |
| 1000 | 0 | 0.00 | 0.00 | 2.69 | 1.86 |
| 1000 | 50 | 0.73 | 0.55 | 2.43 | 1.81 |
| 1000 | 250 | 6.15 | 2.48 | 1.76 | 1.67 |
Incubations were performed with 0.5 mg human liver microsome (HL 3926) at 37°C for 15 min, and metabolite formation independently measured for each substrate.
ND: not detectable, limit of detection is <0.01 nmol/min/mg.