Vasorelaxant and antiplatelet activity of 4,7-dimethyl-1,2,5-oxadiazolo[3,4-<i>d</i>]pyridazine 1,5,6-trioxide: role of soluble guanylate cyclase, nitric oxide and thiols
作者:Alexander Ya Kots、Mikhail A Grafov、Yuri V Khropov、Vasily L Betin、Natalya N Belushkina、Olga G Busygina、Marina Yu Yazykova、Igor V Ovchinnikov、Alexander S Kulikov、Nina N Makhova、Natalya A Medvedeva、Tamara V Bulargina、Irina S Severina
DOI:10.1038/sj.bjp.0703156
日期:2000.3
Certain heterocyclic N‐oxides are vasodilators and inhibitors of platelet aggregation. The pharmacological activity of the furoxan derivative condensed with pyridazine di‐N‐oxide 4,7‐dimethyl‐1,2,5‐oxadiazolo[3,4‐d]pyridazine 1,5,6‐trioxide (FPTO) and the corresponding furazan (FPDO) was studied.
FPTO reacted with thiols generating nitrite (NO), S‐nitrosoglutathione and hydroxylamine (nitroxyl) and converted oxyHb to metHb. FPDO did not generate detectable amounts of NO‐like species but reacted with thiols and oxyHb.
FPTO and FPDO haem‐dependently stimulated the activity of soluble guanylate cyclase (sGC) and this stimulation was inhibited by 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ) and by 0.1 mM dithiothreitol.
FPTO relaxed noradrenaline‐precontracted aortic rings and its concentration‐response curve was biphasic (pIC50=9.03±0.13 and 5.85±0.06). FPDO was significantly less potent vasodilator (pIC50=5.19±0.14). The vasorelaxant activity of FPTO and FPDO was inhibited by ODQ. oxyHb significantly inhibited only FPTO‐dependent relaxation.
FPTO and FPDO were equipotent inhibitors of ADP‐induced platelet aggregation (IC50=0.63±0.15 and 0.49±0.05 μM, respectively). The antiplatelet activity of FPTO (but not FPDO) was partially suppressed by oxyHb. The antiaggregatory effects of FPTO and FPDO were only partially blocked by sGC inhibitors.
FPTO and FPDO (10–20 μM) significantly increased cyclic GMP levels in aortic rings and platelets and this increase was blocked by ODQ.
Thus, FPTO can generate NO and, like FPDO, reacts with thiols and haem. The vasorelaxant activity of FPTO and FPDO is sGC‐dependent and a predominant role is played by NO at FPTO concentrations below 1 μM. On the contrary, inhibition of platelet aggregation is only partially related to sGC activation.
British Journal of Pharmacology (2000) 129, 1163–1177; doi:10.1038/sj.bjp.0703156
某些异杂环氮氧化物是血管扩张剂和血小板聚集抑制剂。研究了呋草烷衍生物与吡啶二氮氧化物缩合的4,7-二甲基-1,2,5-氧杂二唑-[3,4-d]吡啶-1,5,6-三氧化物(FPTO)及其相应的呋喃基化合物(FPDO)的药理活性。
FPTO与硫醇反应,产生亚硝酸盐(NO)、S-硝基谷胱甘肽和羟胺(亚硝酸盐),并且将氧合血红蛋白(oxyHb)转化为高铁血红蛋白(metHb)。FPDO未产生可检测的NO样物质,但与硫醇和oxyHb反应。
FPTO和FPDO依赖血红素刺激可溶性鸟苷酸环化酶(sGC)的活性,这种刺激作用被1H-[1,2,4]氧杂二唑-[4,3-a]喹喔啉-1-酮(ODQ)和0.1 mM二硫苏糖醇抑制。
FPTO松弛了肾上腺素引起的主动脉环收缩,其浓度-反应曲线呈双相(pIC50=9.03±0.13 和 5.85±0.06)。FPDO作为血管扩张剂的效力显著较低(pIC50=5.19±0.14)。FPTO和FPDO的血管舒张活性被ODQ抑制。oxyHb显著抑制仅依赖FPTO的松弛作用。
FPTO和FPDO对ADP诱导的血小板聚集具有相同的抑制效力(IC50=0.63±0.15 和 0.49±0.05 μM)。FPTO(而非FPDO)的抗血小板活性被oxyHb部分抑制。FPTO和FPDO的抗聚集作用仅部分被sGC抑制剂阻断。
FPTO和FPDO(10–20 μM)显著增加了主动脉环和血小板中的环GMP水平,这种增加被ODQ阻断。
因此,FPTO可以产生NO,并且与FPDO一样与硫醇和血红素反应。FPTO和FPDO的血管舒张作用依赖于sGC,而NO在FPTO浓度低于1 μM时起主要作用。相反,血小板聚集的抑制仅部分与sGC活化相关。
British Journal of Pharmacology (2000) 129, 1163–1177; doi:10.1038/sj.bjp.0703156