Ignarro L J, Gold M E, Buga G M, Byrns R E, Wood K S, Chaudhuri G, Frank G
Department of Pharmacology, UCLA School of Medicine 90024.
Circ Res. 1989 Feb;64(2):315-29. doi: 10.1161/01.res.64.2.315.
The objective of this study was to elucidate the mechanism by which polyamino acids containing L-arginine, L-lysine or L-ornithine cause endothelium-dependent relaxation of bovine intrapulmonary artery and vein. Basic but not acidic or neutral polypeptides ranging in average molecular weights from 17 to 225 kDa elicited time- and concentration-dependent relaxation and cyclic GMP accumulation in precontracted rings of artery and vein by endothelium-dependent mechanisms. Vascular responses were markedly inhibited by oxyhemoglobin, methylene blue, or potassium. The basic polyamino acids stimulated the formation and/or release of an endothelium-derived relaxing factor (EDRF) identified as nitric oxide (NO) in perfused segments of both artery and vein as assessed by bioassay. The polyamino acids and A23187 released a similar endothelium-derived NO (EDNO) from artery and vein, as assessed by the similar half-life (3-5 seconds), antagonism by superoxide anion or oxyhemoglobin, enhancement by superoxide dismutase, and lack of influence by indomethacin. The basic polyamino acids elicited potent relaxant responses with EC50 values ranging from 3 x 10(-9) to 2 x 10(-7) M, and a direct correlation was obtained between molecular weight and relaxation potency irrespective of the basic amino acid incorporated. Prolonged contact of arterial or venous rings with basic polyamino acids resulted in the rapid development of marked refractoriness to relaxation and cyclic GMP formation on addition of polyamino acid. Moreover, refractoriness developed to the vascular responses of other endothelium-dependent vasodilators but not to glyceryl trinitrate or isoproterenol. The mechanism of refractory responses was attributed to interference with EDNO formation and release as assessed by bioassay and chemical assay. The hypothesis is forwarded that the basic polyamino acids serve as partial substrates for the enzyme system that catalyzes the conversion of L-arginine to NO. Prolonged contact between substrate and enzyme results in enzyme desensitization and the development of refractoriness or a form of tolerance to vasodilators whose action is mediated by EDNO.
本研究的目的是阐明含有L-精氨酸、L-赖氨酸或L-鸟氨酸的多聚氨基酸引起牛肺内动脉和静脉内皮依赖性舒张的机制。平均分子量在17至225 kDa之间的碱性而非酸性或中性多肽，通过内皮依赖性机制在预先收缩的动脉和静脉环中引起时间和浓度依赖性舒张以及环鸟苷酸（cGMP）积累。血管反应被氧合血红蛋白、亚甲蓝或钾显著抑制。通过生物测定评估，碱性多聚氨基酸在动脉和静脉的灌注节段中刺激了一种被鉴定为一氧化氮（NO）的内皮源性舒张因子（EDRF）的形成和/或释放。通过相似的半衰期（3 - 5秒）、超氧阴离子或氧合血红蛋白的拮抗作用、超氧化物歧化酶的增强作用以及吲哚美辛的无影响评估，多聚氨基酸和A23187从动脉和静脉释放出相似的内皮源性NO（EDNO）。碱性多聚氨基酸引发了强效的舒张反应，其半数有效浓度（EC50）值范围为3×10⁻⁹至2×10⁻⁷ M，并且无论掺入何种碱性氨基酸，分子量与舒张效力之间都存在直接相关性。动脉或静脉环与碱性多聚氨基酸的长时间接触导致在添加多聚氨基酸时迅速产生对舒张和cGMP形成的明显不应性。此外，对其他内皮依赖性血管舒张剂的血管反应产生了不应性，但对硝酸甘油或异丙肾上腺素没有不应性。通过生物测定和化学测定评估，不应性反应的机制归因于对EDNO形成和释放的干扰。提出的假设是，碱性多聚氨基酸作为催化L-精氨酸转化为NO的酶系统的部分底物。底物与酶的长时间接触导致酶脱敏以及对由EDNO介导其作用的血管舒张剂产生不应性或某种形式的耐受性。
