Kelm M, Schrader J
University of Düsseldorf, Physiologisches Institut I, FRG.
Circ Res. 1990 Jun;66(6):1561-75. doi: 10.1161/01.res.66.6.1561.
A specific difference-spectrophotometric method was used to measure nitric oxide (NO) release into the coronary effluent perfusate of isolated, constant-flow-perfused guinea pig hearts. Authentic NO applied into the coronary circulation decreased vascular resistance dose dependently and enhanced coronary release of cyclic GMP (cGMP) fivefold. Increasing oxygen tension in aqueous solutions from 150 to 700 mm Hg decreased NO half-life (5.6 seconds) by 32%. During single passage through the intact coronary system, 86% of the infused NO was converted to nitrite ions. Oxidation of NO was more than 30 times faster within the heart than in aqueous solution. Endogenously formed NO was constantly released into the coronary effluent perfusate at a rate of 161 +/- 11 pmol/min. The NO scavenger oxyhemoglobin and methylene blue increased coronary resistance and decreased cGMP release (basal release, 342 +/- 4 fmol/min), whereas superoxide dismutase reduced coronary resistance. L-Arginine (10(-5) M) slightly decreased coronary perfusion pressure and enhanced release of cGMP. NG-Monomethyl L-arginine (10(-4) M) reduced basal release of NO and cGMP by 26% and 31%, respectively, paralleled by a coronary vasoconstriction. Bradykinin in the physiological range from 5 x 10(-11) M to 10(-7) M dilated coronary resistance vessels, which was paralleled by the release of NO and cGMP. Onset of NO release preceded onset of coronary vasodilation in all cases. Upon stimulation with bradykinin, amounts of endogenously formed NO were within the same range as the dose-response curves for exogenously applied NO both for changes in coronary resistance and cGMP release. Acetylcholine (10(-5) M), ATP (10(-5) M), and serotonin (10(-8) M) increased the rate of NO and cGMP release, resulting in coronary vasodilation. Our data suggest the following: 1) NO, the most rapidly acting vasodilator presently known, is metabolized within the heart mainly to nitrite and exhibits a half-life of only 0.1 second; 2) in the unstimulated heart, basal formation of NO may play an important role in setting the resting tone of coronary resistance vessels; 3) the kinetics and quantities of NO formation suggest that NO is causally involved in the bradykinin-induced coronary vasodilation; and 4) amounts of NO formed within the heart stimulated with ATP, acetylcholine, and serotonin are effective for vasodilation.
采用一种特定的差示分光光度法来测定一氧化氮（NO）释放到离体、恒流灌注的豚鼠心脏冠状动脉流出灌注液中的量。向冠状动脉循环中注入纯NO可使血管阻力剂量依赖性降低，并使冠状动脉中环鸟苷酸（cGMP）的释放增加5倍。将水溶液中的氧张力从150毫米汞柱提高到700毫米汞柱，可使NO半衰期（5.6秒）缩短32%。在单次通过完整的冠状动脉系统过程中，注入的NO中有86%转化为亚硝酸根离子。心脏内NO的氧化速度比在水溶液中快30倍以上。内源性生成的NO以161±11皮摩尔/分钟的速率持续释放到冠状动脉流出灌注液中。NO清除剂氧合血红蛋白和亚甲蓝可增加冠状动脉阻力并降低cGMP释放（基础释放量为342±4飞摩尔/分钟），而超氧化物歧化酶可降低冠状动脉阻力。L-精氨酸（10⁻⁵摩尔/升）可轻微降低冠状动脉灌注压并增强cGMP释放。NG-单甲基-L-精氨酸（10⁻⁴摩尔/升）可分别使NO和cGMP的基础释放量降低26%和31%，同时伴有冠状动脉血管收缩。生理范围内浓度从5×10⁻¹¹摩尔/升到10⁻⁷摩尔/升的缓激肽可使冠状动脉阻力血管扩张，同时伴有NO和cGMP的释放。在所有情况下，NO释放的开始均先于冠状动脉血管舒张的开始。在用缓激肽刺激时，内源性生成的NO量与外源性应用NO时冠状动脉阻力和cGMP释放变化的剂量反应曲线处于同一范围内。乙酰胆碱（10⁻⁵摩尔/升）、ATP（10⁻⁵摩尔/升）和5-羟色胺（10⁻⁸摩尔/升）可增加NO和cGMP的释放速率，导致冠状动脉血管舒张。我们的数据表明：1）NO是目前已知作用最快的血管舒张剂，在心脏内主要代谢为亚硝酸盐，半衰期仅为0.1秒；2）在未受刺激的心脏中，NO的基础生成可能在设定冠状动脉阻力血管的静息张力方面起重要作用；3）NO生成的动力学和量表明，NO在缓激肽诱导的冠状动脉血管舒张中起因果作用；4）在受ATP、乙酰胆碱和5-羟色胺刺激的心脏内生成的NO量对血管舒张有效。
