Kowaluk E A, Fung H L
Department of Pharmaceutics, School of Pharmacy, State University of New York, Buffalo.
J Pharmacol Exp Ther. 1990 Dec;255(3):1256-64.
S-nitrosothiols are potent vasodilators in vivo and in vitro, and have recently been proposed as possible endogenous precursors of endothelium-derived nitric oxide (NO). NO release from S-nitrosothiols has generally been assumed to be spontaneous, but this has not been proven. This hypothesis was examined by altering the NO release profiles of two S-nitrosothiols, those of S-nitroso-N-acetylpenicillamine (SNAP) and S-nitroso-glutathione (GSNO), and observing their relaxation potency on isolated endothelium-denuded rat aortic rings. Spontaneous degradation of SNAP and GSNO in tissue bathing medium (monitored by high-performance liquid chromatography) and the associated NO release (assessed by chemiluminescence detection of headspace NO) were enhanced in the presence of 100 microM N-acetylpenicillamine and inhibited in the presence of 100 U/ml superoxide dismutase. However, the relaxant effects of SNAP and GSNO were enhanced in the presence of superoxide dismutase, and diminished in the presence of N-acetylpenicillamine. In addition, the relaxation potencies of SNAP, GSNO, S-nitrosocystein, S-nitroso-N-acetylcysteine and S-nitroso-coenzyme A were not correlated with spontaneous NO generation. These findings therefore argue against spontaneous liberation of NO as a predominant mechanism of S-nitrosothiol action. The highly polar SNAP, GSNO, S-nitrosocysteine and S-nitroso-N-acetylcysteine (octanol, pH 7.4 buffer partition coefficient from less than .025-.052) and the bulky and polar S-nitroso-coenzyme A (MW 797) have similar relaxation potencies, indicating that intracellular penetration of intact S-nitrosothiols may not be required for activity. NO generation from SNAP was examined in subcellular fractions of bovine coronary arterial smooth muscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)
S-亚硝基硫醇在体内和体外都是强效血管舒张剂，最近被认为可能是内皮衍生一氧化氮（NO）的内源性前体。一般认为S-亚硝基硫醇释放NO是自发的，但这尚未得到证实。通过改变两种S-亚硝基硫醇（S-亚硝基-N-乙酰青霉胺（SNAP）和S-亚硝基谷胱甘肽（GSNO））的NO释放曲线，并观察它们对离体去内皮大鼠主动脉环的舒张能力，对这一假设进行了检验。在100微摩尔N-乙酰青霉胺存在下，组织浴液中SNAP和GSNO的自发降解（通过高效液相色谱监测）及相关的NO释放（通过顶空气相NO的化学发光检测评估）增强，而在100单位/毫升超氧化物歧化酶存在下则受到抑制。然而，在超氧化物歧化酶存在下，SNAP和GSNO的舒张作用增强，而在N-乙酰青霉胺存在下则减弱。此外，SNAP、GSNO、S-亚硝基半胱氨酸、S-亚硝基-N-乙酰半胱氨酸和S-亚硝基辅酶A的舒张能力与自发产生的NO无关。因此，这些发现反对将NO的自发释放作为S-亚硝基硫醇作用的主要机制。高极性的SNAP、GSNO、S-亚硝基半胱氨酸和S-亚硝基-N-乙酰半胱氨酸（辛醇，pH 7.4缓冲液分配系数小于0.025 - 0.052）以及体积大且极性的S-亚硝基辅酶A（分子量797）具有相似的舒张能力，这表明完整的S-亚硝基硫醇发挥活性可能不需要细胞内渗透。在牛冠状动脉平滑肌细胞的亚细胞组分中检测了SNAP产生NO的情况。（摘要截短于250字）
