Alonso-Galicia M, Sun C W, Falck J R, Harder D R, Roman R J
Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Am J Physiol. 1998 Sep;275(3):F370-8. doi: 10.1152/ajprenal.1998.275.3.F370.
The present study examined the contribution of elevations in cGMP versus inhibition of cytochrome P-4504A enzymes and the production of the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE) to the vasodilator actions of NO in renal arterioles. The NO donor sodium nitroprusside (SNP) at 10(-5), 10(-4), and 10(-3) M reduced the production of 20-HETE in microsomes prepared from renal arterioles to 80 +/- 2, 43 +/- 5, and 7 +/- 1% of control, respectively (n = 4). In other experiments, the vasodilator response to SNP (10(-7) to 10(-3) M) was examined in rat renal interlobular arteries (<90 micron ID), preconstricted with phenylephrine (1 microM) under control conditions and after blockade of the cGMP and P-4504A pathways. Inhibition of guanylyl cyclase with 1H-[1,2, 4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) (10 microM, n = 6) or of cGMP-dependent protein kinase with 8R,9S, 11S-(-)-9-methoxy-carbamyl-8-methyl-2,3,9,10-tetrahydro-8, 11-epoxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cycloocta-(c, d, e)-trinden-1-one (KT-5823, 1 microM; n = 5) attenuated the vasodilator response to SNP by 26 and 30%, respectively. In contrast, inhibition of the endogenous production of 20-HETE with a suicide substrate, irreversible inhibitor [17-octadecynoic acid (17-ODYA), 1 microM, n = 5], or a selective, competitive inhibitor of 20-HETE formation (dibromo-dodecenyl-methylsulfimide, 25 microM, n = 5) markedly impaired the vasodilator response to SNP by 76 and 78%, respectively. Similarly, when 20-HETE levels were fixed at 100 nM (n = 6), the response to SNP was attenuated by 73%. Blockade of both pathways with ODQ and 17-ODYA completely abolished the response to SNP (n = 6). These results indicate that the vasodilator response to NO is largely cGMP independent and that inhibition of 20-HETE formation contributes to the cGMP-independent effects of NO in the renal microcirculation.
本研究探讨了环磷酸鸟苷（cGMP）升高、细胞色素P - 4504A酶抑制以及血管收缩剂20 - 羟基二十碳四烯酸（20 - HETE）生成对肾小动脉中一氧化氮（NO）舒张血管作用的贡献。10⁻⁵、10⁻⁴和10⁻³ M的NO供体硝普钠（SNP）分别将从肾小动脉制备的微粒体中20 - HETE的生成量降低至对照的80±2%、43±5%和7±1%（n = 4）。在其他实验中，在对照条件下以及阻断cGMP和P - 4504A途径后，用去氧肾上腺素（1 μM）预收缩大鼠肾小叶间动脉（内径<90微米），检测其对SNP（10⁻⁷至10⁻³ M）的舒张血管反应。用1H - [1,2,4]恶二唑[4,3 - a]喹喔啉 - 1 - 酮（ODQ，10 μM，n = 6）抑制鸟苷酸环化酶或用8R,9S,11S - (-) - 9 - 甲氧基 - 氨基甲酰 - 8 - 甲基 - 2,3,9,10 - 四氢 - 8,11 - 环氧 - 1H,8H,11H - 2,7b,11a - 三氮杂二苯并 - (a,g) - 环辛 - (c,d,e) - 三茚 - 1 - 酮（KT - 5823，1 μM；n = 5）抑制cGMP依赖性蛋白激酶，分别使对SNP的舒张血管反应减弱26%和30%。相反，用自杀底物、不可逆抑制剂[17 - 十八炔酸（17 - ODA），1 μM，n = 5]或20 - HETE形成的选择性竞争性抑制剂（二溴 - 十二碳烯基 - 甲基磺酰亚胺，25 μM，n = 5）抑制内源性20 - HETE的生成，分别使对SNP的舒张血管反应显著减弱76%和78%。同样，当20 - HETE水平固定在100 nM时（n = 6），对SNP的反应减弱了73%。用ODQ和17 - ODA阻断两条途径完全消除了对SNP的反应（n = 6）。这些结果表明，对NO的舒张血管反应在很大程度上不依赖于cGMP，并且抑制20 - HETE的形成有助于NO在肾微循环中产生不依赖于cGMP的效应。
