Gupte S A, Rupawalla T, Phillibert D, Wolin M S
Department of Physiology, New York Medical College, Valhalla, New York 10595, USA.
Am J Physiol. 1999 Dec;277(6):L1124-32. doi: 10.1152/ajplung.1999.277.6.L1124.
The hemoprotein oxidant ferricyanide (FeCN) converts the iron of the heme on soluble guanylate cyclase (sGC) from Fe(2+) to Fe(3+), which prevents nitric oxide (NO) from binding the heme and stimulating sGC activity. This study uses FeCN to examine whether modulation of the redox status of the heme on sGC influences the relaxation of endothelium-removed bovine pulmonary arteries (BPA) to NO. Pretreatment of the homogenate of BPA with 50 microM FeCN resulted in a loss of stimulation of sGC activity by the NO donor 10 microM S-nitroso-N-acetylpenicillamine (SNAP). In the FeCN-treated homogenate reconcentrated to the enzyme levels in BPA, 100 microM NADPH restored NO stimulation of sGC, and this effect of NADPH was prevented by an inhibitor of flavoprotein electron transport, 1 microM diphenyliodonium (DPI). In BPA the relaxation to SNAP was not altered by FeCN, inhibitors of NADPH generation by the pentose phosphate pathway [250 microM 6-aminonicotinamide (6-AN) and 100 microM epiandrosterone (Epi)], or 1 microM DPI. However, the combination of FeCN with 6-AN, Epi, or DPI inhibited (P < 0.05) relaxation to SNAP without significantly altering the relaxation of BPA to forskolin. The inhibitory effects of 1 microM 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalin-1-one (a probe that appears to convert NO-heme of sGC to its Fe(3+)-heme form) on relaxation to SNAP were also enhanced by DPI. These observations suggest that a flavoprotein containing NADPH oxidoreductase may influence cGMP-mediated relaxation of BPA to NO by maintaining the heme of sGC in its Fe(2+) oxidation state.
血红素蛋白氧化剂铁氰化物（FeCN）可将可溶性鸟苷酸环化酶（sGC）上血红素的铁从Fe(2+)转化为Fe(3+)，这会阻止一氧化氮（NO）与血红素结合并刺激sGC活性。本研究使用FeCN来检测sGC上血红素氧化还原状态的调节是否会影响去除内皮的牛肺动脉（BPA）对NO的舒张反应。用50微摩尔FeCN预处理BPA匀浆会导致NO供体10微摩尔S-亚硝基-N-乙酰青霉胺（SNAP）对sGC活性的刺激作用丧失。在重新浓缩至BPA中酶水平的FeCN处理的匀浆中，100微摩尔NADPH可恢复NO对sGC的刺激作用，而黄素蛋白电子传递抑制剂1微摩尔二苯基碘鎓（DPI）可阻止NADPH的这种作用。在BPA中，FeCN、磷酸戊糖途径生成NADPH的抑制剂[250微摩尔6-氨基烟酰胺（6-AN）和100微摩尔表雄酮（Epi）]或1微摩尔DPI均未改变对SNAP的舒张反应。然而，FeCN与6-AN、Epi或DPI联合使用会抑制（P<0.05）对SNAP的舒张反应，而对BPA对福斯可林的舒张反应无明显影响。1微摩尔1H-[1,2,4]恶二唑并[4,3-a]喹喔啉-1-酮（一种似乎可将sGC的NO-血红素转化为其Fe(3+)-血红素形式的探针）对SNAP舒张反应的抑制作用也会被DPI增强。这些观察结果表明，含有NADPH氧化还原酶的黄素蛋白可能通过将sGC的血红素维持在其Fe(2+)氧化状态来影响cGMP介导的BPA对NO的舒张反应。
