Effects of NO donors on the kinetic parameters of P450 substrates Microsomes were obtained after perfusion of isolated rat livers for 1 h in the absence (control) or presence of 200 μM NO donors SNP or ISDN (n = 4/group). Kinetic parameters were estimated using equations described in the text. Values are mean ± S.E.
Enzyme/Substrate/Metabolite | Group | Kinetic Parameters | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| High Affinity Component | Low Affinity Component | Overall | ||||||||||||||||||
| Km(1) | Vmax(1)
a
| n(1) | CLint(1) | Km(2) | Vmax(2)
a
| n(2) | CLint(2) | CLmax | CLtotal | |||||||||||
| μM | μl/min/mg protein | μM | μl/min/mg protein | μl/min/mg protein | ||||||||||||||||
| 3A2 | Control | 51 ± 2 | 5.5 ± 0.6 | 1 | 110 ± 12 | —b | — | — | — | — | 110 ± 12 | |||||||||
| T | SNP | 19 ± 2* | 1.8 ± 0.3* | 1 | 93 ± 12 | — | — | — | — | — | 93 ± 12 | |||||||||
| 6β-HT | ISDN | 29 ± 2* | 3.6 ± 0.6* | 1 | 130 ± 26 | — | — | — | — | — | 130 ± 26 | |||||||||
| 2C11 | Control | 37 ± 2 | 2.2 ± 0.3 | 1 | 60 ± 10 | — | — | — | — | — | 60 ± 10 | |||||||||
| T | SNP | 8.5 ± 0.7* | 0.78 ± 0.06* | 1 | 92 ± 3 | — | — | — | — | — | 92 ± 3 | |||||||||
| 16α-HT | ISDN | 8.4 ± 1.5* | 0.96 ± 0.01* | 1 | 130 ± 20* | — | — | — | — | — | 130 ± 20* | |||||||||
| 2D1 | Control | 0.91 ± 0.38 | 0.43 ± 0.06 | 1 | 860 ± 320 | 35 ± 4 | 2.0 ± 0.1 | 1 | 59 ± 8 | — | 920 ± 320 | |||||||||
| DM | SNP | 0.76 ± 0.19 | 0.41 ± 0.05 | 1 | 690 ± 230 | 99 ± 24* | 0.25 ± 0.04* | 1 | 3.2 ± 0.9* | — | 700 ± 230 | |||||||||
| DT | ISDN | 1.0 ± 0.1 | 0.62 ± 0.02* | 1 | 630 ± 60 | 90 ± 22 | 0.59 ± 0.03* | 1 | 8.2 ± 2.5* | — | 640 ± 60 | |||||||||
| 3A2 | Control | 54 ± 2 | 6.4 ± 0.4 | 1.3 ± 0.0 | — | — | — | — | — | 74 ± 3 | — | |||||||||
| DM | SNP | 130 ± 13* | 1.0 ± 0.2* | 1.3 ± 0.0 | — | — | — | — | — | 9.1 ± 1.1* | — | |||||||||
| MXM | ISDN | 120 ± 13* | 3.2 ± 0.2* | 1.1 ± 0.1* | — | — | — | — | — | 24 ± 3* | — | |||||||||
| 2E1 | Control | — | — | — | — | 140 ± 8 | 1.9 ± 0.1 | 1.2 ± 0.0 | — | 8.8 ± 0.4 | — | |||||||||
| CLZ | SNP | 4.6 ± 2.5 | 0.022 ± 0.006 | 1 | 7.7 ± 2.3 | 390 ± 40* | 0.72 ± 0.11* | 1.4 ± 0.1 | — | 2.8 ± 0.2* | — | |||||||||
| 6-HCLZ | ISDN | — | — | — | — | 190 ± 8 | 1.2 ± 0.1* | 1.2 ± 0.0 | — | 4.7 ± 0.5* | — | |||||||||
| 2B1/2 | Control | 0.081 ± 0.019 | 2.9 ± 0.6 | 1 | 36 ± 2 | 1.5 ± 0.2 | 26 ± 3 | 1 | 19 ± 3 | — | 54 ± 3 | |||||||||
| BR | SNP | 0.086 ± 0.003 | 2.8 ± 0.2 | 1 | 32 ± 2 | 0.54 ± 0.06 | 12 ± 2 | 5.8 ± 0.2 | — | 36 ± 3 | — | |||||||||
| R | ISDN | 0.085 ± 0.016 | 0.86 ± 0.15* | 1 | 11 ± 2* | 1.6 ± 0.3 | 8.1 ± 0.5** | 1 | 6.0 ± 1.4* | — | 17 ± 3** | |||||||||
| 1A1/2 | Control | 0.014 ± 0.002 | 4.6 ± 0.9 | 1 | 330 ± 48 | 0.63 ± 0.03 | 67 ± 9 | 1 | 110 ± 18 | — | 440 ± 65 | |||||||||
| ER | ISDN | 0.044 ± 0.01** | 4.5 ± 1.2 | 1 | 130 ± 45** | 0.076 ± 0.01** | 8.7 ± 2.8** | 1 | 110 ± 33 | — | 230 ± 42** | |||||||||
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↵* Significantly different from control, P < 0.05; analysis of variance, followed by Fisher's test
↵** Significantly different from control, P < 0.05; unpaired t test
↵ a Except for CYP2B1/2 and 1A1/2, which are expressed as pmol/mg protein/min, rates are expressed as nmol/mg protein/min
↵ b —, not applicable to the selected model