McGuire J J, Anderson D J, McDonald B J, Narayanasami R, Bennett B M
Department of Pharmacology and Toxicology, Queen's University, Kingston, Ontario, Canada.
Biochem Pharmacol. 1998 Oct 1;56(7):881-93. doi: 10.1016/s0006-2952(98)00216-0.
We reported previously that the flavoprotein inhibitor diphenyleneiodonium sulfate (DPI) irreversibly inhibited the metabolic activation of glyceryl trinitrate (GTN) in isolated aorta, possibly through inhibition of vascular NADPH-cytochrome P450 reductase (CPR). We report that the content of CPR represents 0.03 to 0.1% of aortic microsomal protein and that DPI caused a concentration- and time-dependent inhibition of purified cDNA-expressed rat liver CPR and of aortic and hepatic microsomal NADPH-cytochrome c reductase activity. Purified CPR incubated with NADPH and GTN under anaerobic, but not aerobic conditions formed the GTN metabolites glyceryl-1,3-dinitrate (1,3-GDN) and glyceryl-1,2-dinitrate (1,2-GDN). GTN biotransformation by purified CPR and by aortic and hepatic microsomes was inhibited > 90% after treatment with DPI and NADPH. DPI treatment also inhibited the production of activators of guanylyl cyclase formed by hepatic microsomes. We also tested the effect of DPI on the hemodynamic-pharmacokinetic properties of GTN in conscious rats. Pretreatment with DPI (2 mg/kg) significantly inhibited the blood pressure lowering effect of GTN and inhibited the initial appearance of 1,2-GDN (1-5 min) and the clearance of 1,3-GDN. These data suggest that the rapid initial formation of 1,2-GDN is related to mechanism-based GTN biotransformation and to enzyme systems sensitive to DPI inhibition. We conclude that vascular CPR is a site of action for the inhibition by DPI of the metabolic activation of GTN, and that vascular CPR is a novel site of GTN biotransformation that should be considered when investigating the mechanism of GTN action in vascular tissue.
我们之前报道过，黄素蛋白抑制剂硫酸二苯撑碘鎓（DPI）可不可逆地抑制离体主动脉中甘油三硝酸酯（GTN）的代谢活化，可能是通过抑制血管NADPH-细胞色素P450还原酶（CPR）实现的。我们报道CPR的含量占主动脉微粒体蛋白的0.03%至0.1%，并且DPI对纯化的cDNA表达的大鼠肝脏CPR以及主动脉和肝脏微粒体的NADPH-细胞色素c还原酶活性产生浓度和时间依赖性抑制。在厌氧而非需氧条件下，纯化的CPR与NADPH和GTN一起孵育会形成GTN代谢产物甘油-1,3-二硝酸酯（1,3-GDN）和甘油-1,2-二硝酸酯（1,2-GDN）。用DPI和NADPH处理后，纯化的CPR以及主动脉和肝脏微粒体对GTN的生物转化被抑制>90%。DPI处理还抑制了肝脏微粒体形成的鸟苷酸环化酶激活剂的产生。我们还测试了DPI对清醒大鼠中GTN血液动力学-药代动力学特性的影响。用DPI（2mg/kg）预处理可显著抑制GTN的降压作用，并抑制1,2-GDN的初始出现（1-5分钟）以及1,3-GDN的清除。这些数据表明，1,2-GDN的快速初始形成与基于机制的GTN生物转化以及对DPI抑制敏感的酶系统有关。我们得出结论，血管CPR是DPI抑制GTN代谢活化的作用位点，并且血管CPR是GTN生物转化的一个新位点，在研究GTN在血管组织中的作用机制时应予以考虑。
