Inhibitory effects of CCBs on testosterone 6β-hydroxylase activity in human liver microsomes before and after dialysis
| Initial Concentration | Before Dialysis | After Dialysis | |||
|---|---|---|---|---|---|
| Without NADPH | With NADPH | Without NADPH | With NADPH | ||
| μM | |||||
| Control | 0 | 100 ± 0.5 | 100 ± 1 | 100 ± 0.8 | 100 ± 1 |
| Nicardipine | 2 | 66 ± 0.8 | 20 ± 0.5 | 91 ± 0.8 | 116 ± 1 |
| Verapamil | 10 | 91 ± 1 | 24 ± 0.4 | 101 ± 2 | 111 ± 1 |
| Diltiazem | 25 | 98 ± 1 | 47 ± 0.3 | 101 ± 3 | 79 ± 1 |
| Ketoconazole | 1 | 22 ± 1 | 32 ± 0.4 | 85 ± 0.2 | 93 ± 3 |
| Mibefradil | 2 | 87 ± 2 | 5 ± 0.4 | 96 ± 1 | 14 ± 0.4 |
| Ethynylestradiol | 50 | 54 ± 1 | 8 ± 0.3 | 93 ± 1 | 31 ± 0.2 |
| TAO | 50 | 86 ± 1 | 14 ± 0.2 | 98 ± 0.7 | 102 ± 2 |
Results (% of control) are mean ± S.D. of triplicate determinations. Activities were determined before and after dialysis using 250 μM testosterone and after a 5-fold dilution of the incubation mixture after a 30-min preincubation in the presence or absence of NADPH. Control activities (nanomoles per minute per milligram, mean ± S.D., n = 3) before dialysis = 3.5 ± 0.1 and 3.8 ± 0.04 and after dialysis = 3.5 ± 0.04 and 2.9 ± 0.04 with or without NADPH, respectively.