多酚化合物LM49对大鼠离体胸主动脉的舒张作用及机制

Vasorelaxant effects and mechanism of polyphenol compound LM49 on isolated thoracic aorta of rats

目的研究多酚化合物2,4′,5′-三羟基-5,2′-二溴二苯甲酮(LM49)对大鼠离体胸主动脉的舒张作用及机制。方法取大鼠胸主动脉血管环,以舒张血管百分比为指标,考察不同浓度LM49对去甲肾上腺素(1×10^(-6)mol/L)及KCl(60 mmol/L)预收缩的内皮完整或去内皮血管环的舒张作用;分别以一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(L-NAME,0.1 mmol/L)、环氧合酶抑制剂吲哚美辛(1×10^(-5)mol/L)和4种钾通道阻滞剂[BaCl_(2)(0.1 mmol/L)、四乙基胺(5 mmol/L)、4-氨基吡啶(0.1 mmol/L)、格列苯脲(1×10^(-5)mol/L)]预孵育血管环,考察不同浓度LM49对血管环的舒张作用。以血管收缩百分率为指标,在无钙条件下,分别以KCl(60 mmol/L)、去甲肾上腺素(1×10^(-6)mol/L)和钙通道阻滞剂维拉帕米(1×10^(-6)mol/L)、肌浆网Ca^(2+)-腺苷三磷酸(ATP)酶泵抑制剂毒胡萝卜素(1×10^(-6)mol/L)诱发血管环内钙释放后,再分别累积加入CaCl_(2),考察LM49对CaCl_(2)导致外钙内流引起的血管收缩的影响。结果3×10^(-6)、5×10^(-6)、1×10^(-5)mol/L LM49对去甲肾上腺素和KCl预收缩的血管环具有显著舒张作用(P<0.01),且是否去除内皮对LM49舒张血管的作用无显著影响(P>0.05)。经L-NAME、吲哚美辛、四乙基胺和4-氨基吡啶预孵育后,不同浓度的LM49对经去甲肾上腺素预收缩的血管环无显著影响(P>0.05),格列苯脲和BaCl_(2)均可抑制LM49对去甲肾上腺素预收缩血管环的舒张作用(P<0.01)。在无钙条件下,血管环经KCl、去甲肾上腺素、维拉帕米及毒胡萝卜素预孵育后,LM49能抑制CaCl_(2)导致外钙内流引起的收缩(P<0.01)。结论LM49具有显著的血管舒张作用,且无内皮依赖性;其具体机制可能为诱导ATP敏感型钾通道、内向整流型钾通道开放,及抑制细胞外Ca^(2+)通过电压门控钙通道、受体操控钙通道、钙库操纵性钙通道内流。

OBJECTIVE To study the vasorelaxant effects and mechanism of polyphenol compound 2,4′,5′-trihydroxy-5,2′-dibromo-diphenyl-methanone(LM49)on isolated aortic rings of rats.METHODS Thoracic aortic vascular rings of rats were collected.Using the diastolic rate as index,the effects of different concentrations of LM49 on endothelium-intact and endothelium-denuded aortic rings pre-contracted by norepinephrine(NE,1×10^(-6) mol/L)or KCl(60 mmol/L)were investigated.After pre-culturing vascular rings by nitric oxide synthase inhibitor L-nitro-arginine methyl ester(L-NAME,0.1 mmol/L)and cyclooxygenase inhibitor indomethacin(1×10^(-5) mol/L),as well as pre-culturing vascular rings by 4 potassium channel blockers[BaCl_(2)(0.1 mmol/L),tetraethylammonium(TEA,5 mmol/L),4-aminopyridine(4-AP,0.1 mmol/L)and glibenclamide(1×10^(-5) mol/L)],the vasorelaxant effect of different concentrations of LM49 on the vascular rings were investigated by using the same method.With the percentage of vasoconstriction as the index,using KCl(60 mmol/L),NE(1×10^(-6) mol/L),calcium channel blocker verapamil(1×10^(-6) mol/L)and sarcoplasmic reticulum Ca^(2+)-adenosine triphosphate(ATP)enzyme pump inhibitor thacarotene(TG,1×10^(-6)mol/L)to induce the release of calcium in vascular rings in the absence of calcium.CaCl_(2) was added cumulatively,and the effect of LM49 on the vasoconstriction caused by calcium influx induced by CaCl_(2)was investigated.RESULTS 3×10^(-6),5×10^(-6),1×10^(-5) mol/L LM49 had a significant relaxation effect on NE and KCl precontracted vascular rings(P<0.01);whether the endothelium was removed or not had no significant effect on the vasodilation of LM49(P>0.05).After L-NAME,indomethacin,TEA and 4-AP was pre-incubated,different concentrations of LM49 had no significant effects on aortic rings precontracted by NE(P>0.05).Glibenclamide and BaCl_(2)could inhibit the vasorelaxant effects of LM49 on aortic rings precontracted by NE(P<0.01).In the absence of calcium,LM49 could inhibit the contraction caused by calcium influx induced by accumulated CaCl_(2)after pre-incubation with KCl,NE,verapamil and TG(P<0.01).CONCLUSIONS LM49 evokes significant relaxation of isolated aortic vascular rings without endothelium dependence;the mechanism of which is inducing ATP-sensitive potassium channel,inward rectifier potassium channel open and restraining extracellular Ca^(2+) influx via voltage-gated calcium channel,receptor-operated calcium channel and store-operated calcium channel.