Effects of in vivo GTN tolerance on vascular NADPH- and NADH-dependent cytochrome c reductase activity
| Aortic Microsome Preparation | n | NADPH-Cytochrome c Reductase Activity1-a | n | NADH-Cytochrome c Reductase Activity1-b |
|---|---|---|---|---|
| nmol cytochrome c reduced/min/mg protein | nmol cytochrome c reduced/min/mg protein | |||
| Control | 5 | 16.3 ± 2.8 | 5 | 491 ± 47 |
| Control + SOD | 5 | 12.0 ± 3.21-150 | 5 | 475 ± 49 |
| Tolerant | 5 | 16.8 ± 3.5 | 5 | 450 ± 47 |
| Tolerant + SOD | 4 | 11.0 ± 1.41-150 | 5 | 425 ± 401-150 |
Aortic microsomes were prepared from GTN-tolerant rats or from rats treated with “dummy” transdermal GTN patches (control). NADPH- or NADH-dependent cytochrome c reductase activity of microsomal protein (30–50 μg/ml with NADPH or 5–8 μg/ml with NADH) was measured in the absence or presence of exogenously added SOD (300 U/ml).
↵1-a Each value is the mean ± S.D. of two to four measurements for n preparations using five to six rats per preparation.
↵1-b Each value is the mean ± S.D. of measurements in microsomes from five rats.
↵1-150 P < .05 (control versus control + SOD and tolerant versus tolerant + SOD, Student's t test for paired data).