Buus N H, Simonsen U, Pilegaard H K, Mulvany M J
Department of Pharmacology, University of Aarhus, 8000 Aarhus C, Denmark. Department of Thoracic Surgery, Aarhus University Hospital, Aarhus, Denmark.
Br J Pharmacol. 2000 Jan;129(1):184-92. doi: 10.1038/sj.bjp.0703041.
The main purpose of the study was to clarify to which extent nitric oxide (NO) contributes to acetylcholine (ACh) induced relaxation of human subcutaneous small arteries. Arterial segments were mounted in myographs for recording of isometric tension, NO concentration and smooth muscle membrane potential. In noradrenaline-contracted arteries, ACh induced endothelium-dependent relaxations. The NO synthase inhibitor, N(G)-nitro-L-arginine (L-NOARG) had a small significant effect on the concentration-response curves for ACh, and in the presence of L-NOARG, indomethacin only caused a small additional rightward shift in the ACh relaxation. The NO scavenger, oxyhaemoglobin attenuated relaxations for ACh and for the NO donor S-nitroso-N-acetylpenicillamine (SNAP). Inhibition of guanylyl cyclase with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), and inhibition of protein kinase G with beta-phenyl-1, N2-etheno-8-bromoguanosine- 3', 5'- cyclic monophosphorothioate, Rp-isomer, slightly attenuated ACh relaxation, but abolished SNAP induced relaxation. ACh induced relaxation without increases in the free NO concentration. In contrast, for equivalent relaxation, SNAP increased the NO concentration 32+/-8 nM. ACh hyperpolarized the arterial smooth muscle cells with 11.4+/-1.3 mV and 10.5+/-1.3 mV in the absence and presence of L-NOARG, respectively. SNAP only elicited a hyperpolarization of 1.6+/-0.9 mV. In the presence of indomethacin and L-NOARG, ACh relaxation was almost unaffected by lipoxygenase inhibition with nordihydroguaiaretic acid, or cytochrome P450 inhibition with 17-octadecynoic acid or econazole. ACh relaxation was strongly reduced by the combination of charybdotoxin and apamin, but small increments in the extracellular potassium concentration induced no relaxations. The study demonstrates that the NO/L-arginine pathway is present in human subcutaneous small arteries and to a limited extent is involved in ACh induced relaxation. The study also suggests a small contribution of arachidonic acid metabolites. However, ACh relaxation is mainly dependent on a non-NO, non-prostanoid endothelium dependent hyperpolarization. British Journal of Pharmacology (2000) 129, 184 - 192
该研究的主要目的是阐明一氧化氮（NO）在多大程度上有助于乙酰胆碱（ACh）诱导的人皮下小动脉舒张。将动脉段安装在肌动描记器中以记录等长张力、NO浓度和平滑肌膜电位。在去甲肾上腺素收缩的动脉中，ACh诱导内皮依赖性舒张。NO合酶抑制剂N(G)-硝基-L-精氨酸（L-NOARG）对ACh的浓度-反应曲线有轻微但显著的影响，并且在L-NOARG存在的情况下，吲哚美辛仅使ACh舒张的浓度-反应曲线有轻微的额外右移。NO清除剂氧合血红蛋白减弱了ACh和NO供体S-亚硝基-N-乙酰青霉胺（SNAP）的舒张作用。用1H-[1,2,4]恶二唑并[4,3-a]喹喔啉-1-酮（ODQ）抑制鸟苷酸环化酶，并用β-苯基-1,N2-乙烯基-8-溴鸟苷-3',5'-环磷硫代酸酯、Rp-异构体抑制蛋白激酶G，可轻微减弱ACh的舒张作用，但消除了SNAP诱导的舒张作用。ACh诱导舒张但不增加游离NO浓度。相反，为了产生等效的舒张，SNAP使NO浓度增加了32±8 nM。在不存在和存在L-NOARG的情况下，ACh分别使动脉平滑肌细胞超极化11.4±1.3 mV和10.5±1.3 mV。SNAP仅引起1.6±0.9 mV的超极化。在吲哚美辛和L-NOARG存在的情况下，用去甲二氢愈创木酸抑制脂氧合酶，或用17-十八碳炔酸或益康唑抑制细胞色素P450，对ACh舒张几乎没有影响。蝎毒素和蜂毒明肽联合使用可强烈降低ACh舒张，但细胞外钾浓度的小幅增加不会诱导舒张。该研究表明，NO/L-精氨酸途径存在于人皮下小动脉中，并且在一定程度上参与ACh诱导的舒张。该研究还表明花生四烯酸代谢产物的作用较小。然而，ACh舒张主要依赖于非NO、非前列腺素的内皮依赖性超极化。《英国药理学杂志》（2000年）129卷，184 - 192页
