用兔主动脉条研究小蘖碱和硝普钠对几种激动剂作用的影响

用离体家兔主动脉条观察Ber和NP的作用;NP降低血管条的基本张力,明显逆转由PE,HT、5-HT和KCl所引起的收缩,Ber仅逆转PE引起的收缩,对HT,5-HT和KCl引起的收缩无影响,也不影响血管条的基本张力。 Ber和Pra均阻断PE对血管条的收缩作用,两药的IC_(50)分别为30μM和0.2μM。 实验结果表明;NP非特异性逆转几种激动剂所致血管条的收缩,Ber仅逆转PE引起的血管收缩,其作用性质和Pra相似,提示Ber对血管条的α_1-肾上腺素受体具有选择性阻断作用。     

二氢石蒜碱对家兔脑血管的选择性作用

目的观察二氢石蒜碱( dihydrolycorine,DL)对家兔脑血管的选择性作用.方法采用家兔离体基底动脉(BA)、胸主动脉(TA) 及心室乳头肌(PM)标本,记录药物对其张力的影响.结果 DL使BA静息张力升高,尼莫地平(Nim)则使其降低,对TA无影响.NA、KCl所致BA及TA收缩,DL使之呈剂量依赖性松弛,其IC50值对BA分别为(6.69±3.12)×10-4、(3.41±1.52)×10-3 mol*L-1;对TA分别为(1.49±0.59)×10-3、(2.91±0.99)×10-3 mol*L-1.拮抗NA所致基底动脉收缩作用强于KCl.Nim对KCl所致收缩的抑制强于对NA.DL或Nim对电刺激诱发PM的收缩均有剂量依赖性抑制作用,DL对电刺激诱发PM收缩的IC50值高于NA所致BA收缩IC50值.结论 DL对BA有明显的选择性作用,在BA可能存在使该血管平滑肌收缩的α1受体亚型和使之舒张的β受体.DL作用可能与对这些受体的阻断作用相关.这些选择性作用可能有助于改善缺血区的脑血流.     

L-型钙通道参与大鼠动脉收缩反应的异质性

目的研究不同动脉对同一血管收缩剂的反应性是否存在差异,及其与L-型钙通道的关系。方法采用离体血管张力测定实验方法,测定在累积浓度血管收缩剂处理下的大鼠胸主动脉、肾内动脉或冠状动脉的张力变化以及L-型钙通道阻断剂硝苯地平(nifedipine)的影响。结果苯肾上腺素(phenylephrine,Phe)对冠状动脉无明显影响,但可诱导胸主动脉和肾内动脉产生明显的浓度依赖性收缩,胸主动脉的pEC_(50)明显大于肾内动脉(P<0.05);给予硝苯地平孵育后,再给予累积浓度的Phe,胸主动脉收缩的下降幅度大于肾内动脉(P<0.05)。5-羟色胺(5-hydroxy tryptamine,5-HT)对胸主动脉的收缩作用不明显,但可浓度依赖性诱导肾内动脉和冠状动脉收缩;给予硝苯地平孵育后,再给予累积浓度的5-HT,冠状动脉收缩的下降幅度明显大于肾内动脉(P<0.05)。胸主动脉、肾内动脉和冠状动脉均对血栓素A2类似物(9,11-dideoxy-11α,9α-epoxymethanoprostaglandin,U46619)产生浓度依赖性收缩,肾内动脉收缩量效曲线的E_(max)最小(P<0.05),胸主动脉收缩量效曲线pEC_(50)最大(P<0.05)。给予硝苯地平孵育后,再给予累积浓度的U46619,冠状动脉收缩的下降幅度最大,胸主动脉收缩的下降幅度最小。结论大鼠胸主动脉、肾内动脉及冠状动脉对同一血管收缩剂的反应存在异质性,其中L-型钙通道介导的收缩作用也不同。     

地西泮减弱5-羟色胺收缩老年大鼠离体胸主动脉的作用及其机制

目的观察地西泮(DZP)对5-羟色胺(5-HT)诱导收缩的老年大鼠离体胸主动脉环的作用,并探讨其可能的机制。方法采用离体血管张力记录法,观察5-HT对老年大鼠离体胸主动脉环的作用及DZP的影响。结果①5-HT[(0.01～3)×10-5mol/L]对老年大鼠离体胸主动脉环具有浓度依赖性的收缩作用,血管环收缩达最大收缩50%时的药物浓度(EC50)值约为3×10-6mol/L。②在内皮完整的血管环,DZP3×10-6mol/L使5-HT诱导收缩的浓度-效应曲线的最大收缩幅度(Emax)显著降低(与溶剂对照组相比,P<0.01),但去内皮后,DZP对5-HT的缩血管作用无明显影响(P>0.05)。③一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(L-NAME)能减低DZP对5-HT诱导的缩血管作用的减弱作用(P<0.01),但环氧合酶抑制剂吲哚美辛、外周型苯二氮受体(PBR)特异性阻断剂PK11195对DZP的作用无显著影响(P>0.05)。结论 5-HT对老年大鼠离体胸主动脉环具有浓度依赖性的收缩作用。DZP能显著减弱5-HT的缩血管作用,该作用具有内皮依赖性,与内皮产生的一氧化氮有关,但与前列环素无关。DZP的作用不依赖于PBR。     

普罗布考抑制再狭窄与其调节功能性血管重构的关系

目的　研究普罗布考抗动脉成形术后再狭窄与其调节功能性血管重构的关系。方法　用 3 5F球囊导管构建兔动脉粥样硬化动脉成形术后再狭窄模型。动脉成形术 2wk后取其胸主动脉 ,固定染色并进行计算机图像分析 ;观察血管环对乙酰胆碱诱导的舒张百分率 ,然后再观察其对内源性收缩物质去甲肾上腺素 (NA)、KCl以及 5 羟色胺 (5 HT)的收缩反应性。同时 ,在动脉成形术 2wk后留其血清 ,观察普罗布考对动脉成形术后血清一氧化氮 (NO)含量的影响。结果　普罗布考明显增加血管管腔面积 ,减少新生内膜面积 ;可保护动脉成形术后血管的舒张功能 ,保护内皮细胞合成与释放内皮源性舒张因子NO ,降低血管对内源性收缩物质的收缩反应性。结论　普罗布考能提高扩张性血管重塑 ,抑制收缩性血管重塑 ,从而防止动脉成形术后管腔缩窄防止再狭窄的发生     

二氢石蒜碱对家兔脑血管的选择性作用

目的　观察二氢石蒜碱 (dihydrolycorine ,DL)对家兔脑血管的选择性作用。方法　采用家兔离体基底动脉(BA)、胸主动脉 (TA)及心室乳头肌 (PM)标本 ,记录药物对其张力的影响。结果　DL使BA静息张力升高 ,尼莫地平(Nim)则使其降低 ,对TA无影响。NA、KCl所致BA及TA收缩 ,DL使之呈剂量依赖性松弛 ,其IC50 值 :对BA分别为(6 6 9± 3 12 )× 10 -4、(3 4 1± 1 5 2 )× 10 -3 mol·L-1;对TA分别为 (1 4 9± 0 5 9)× 10 -3 、(2 91± 0 99)× 10 -3 mol·L-1。拮抗NA所致基底动脉收缩作用强于KCl。Nim对KCl所致收缩的抑制强于对NA。DL或Nim对电刺激诱发PM的收缩均有剂量依赖性抑制作用 ,DL对电刺激诱发PM收缩的IC50 值高于NA所致BA收缩IC50 值。结论　DL对BA有明显的选择性作用 ,在BA可能存在使该血管平滑肌收缩的α1受体亚型和使之舒张的 β受体。DL作用可能与对这些受体的阻断作用相关。这些选择性作用可能有助于改善缺血区的脑血流     

多柔比星对大鼠离体胸主动脉和颈总动脉血管环的舒张作用及其机制

目的研究多柔比星(DOX)对大鼠离体胸主动脉和颈总动脉血管环的作用及其机制。方法采用离体血管环恒温灌流系统,通过累积加药法每10 min加入DOX依次使其终浓度递增为1,3,10,30和100μmol·L~(-1),观察其对基础状态、去氧肾上腺素(PE,1μmol·L~(-1))和氯化钾(KCl,60 mmol·L~(-1))预收缩的胸主动脉及颈总动脉血管环的作用,并采用左旋硝基精氨酸甲酯(L-NAME)、4-氨基吡啶(4-AP)、溴化四乙铵(TEA)、氯化钡(BaCl_2)、格列苯脲(Gli)、吲哚美辛(Indo)和普萘洛尔预处理探讨其对血管作用的可能机制。结果 DOX对基础状态下及KCl预收缩的胸主动脉和颈总动脉血管环张力无明显影响;DOX可浓度依赖性地舒张PE预收缩的内皮完整胸主动脉和颈总动脉环(P<0.05),且其对去内皮胸主动脉血管环也有舒张作用,但舒张程度弱于内皮完整组(P<0.05);一氧化氮合酶抑制剂L-NAME 0.1 mmol·L~(-1)、电压依赖性钾通道(K_V)抑制剂4-AP 1 mmol·L~(-1)、钙敏感性钾通道(K_(Ca))抑制剂TEA 1 mmol·L~(-1)和内向整流型钾通道(K_(IR))抑制剂BaCl_21 mmol·L~(-1)均可明显抑制DOX的舒血管作用(P<0.05),环氧化酶抑制剂Indo 0.01 mmol·L~(-1)、ATP敏感性钾通道抑制剂Gli 0.01 mmol·L~(-1)和β肾上腺素能受体阻滞剂普萘洛尔0.01 mmol·L~(-1)对DOX舒血管作用无明显影响;DOX 1,10和100μmol·L~(-1)可浓度依赖性减弱无钙液中PE诱发的血管收缩,并可使氯化钙量效曲线右移。结论 DOX对大鼠离体胸主动脉和颈总动脉血管环有浓度依赖性舒张作用,其舒血管机制可能与血管内皮细胞一氧化氮/cGMP途径、K_V、K_(Ca)、K_(IR)、血管平滑肌细胞内钙释放和外钙内流有关。     

内吗啡肽抑制苯肾上腺素和血管紧张素Ⅱ诱导的离体大鼠胸主动脉环收缩

目的:研究吗啡、内吗啡肽-1和内吗啡肽-2对由苯肾上腺素(PE)和血管紧张素(Ang)Ⅱ诱导离体大鼠胸主动脉环收缩的抑制作用.方法:离体血管环张力试验.结果:与对照组相比,吗啡、内吗啡肽-1和内吗啡肽-2的预处理(0.1-10μmol/L)能明显降低由PE(0.1μmol/L)和Aug Ⅱ(1μmol/L)(P<0.01)诱导离体大鼠胸主动脉环的张力,但是不能减少去内皮血管的张力.纳络酮(1μmol/L)能部分阻断内吗啡肽-1和内吗啡肽-2的抑制作用(P<0.01),N~(ω)-nitro-L-arginine(10μmol/L)或血管环去内皮能完全阻断这种作用(P<0.01).结论:内吗啡肽-1和内吗啡肽-2通过纳络酮敏感方式抑制由PE和AngⅡ诱导的离体大鼠胸主动脉环收缩,这种抑制作用可能与血管内皮NO的释放有关.     

萘哌地尔衍生物BWYJ扩张血管效应及其机理研究

目的 :观察萘哌地尔衍生物BWYJ对家兔血管活动的影响 ,并探讨其血管活性机理 ,为该药的开发研究提供基础资料。方法 :采用家兔主动脉收缩的方法 ,观察BWYJ对去甲肾上腺素 (NA)、5 羟色胺(5 HT)和高钾量效曲线的影响 ;应用无Ca2 复Ca2 的实验法 ,以NA和咖啡因为血管收缩剂 ,间接观察BWYJ对细胞内游离钙浓度 ([Ca2 ]i)的影响 ,并分析其可能作用机理。结果 :BWYJ 10 -7、3×10 -7、10 -6mol·L-1使NA量效曲线明显平行右移 ,而最大反应不变 ,pA2 值为 7.6 1。本品 10 -6、10 -5mol·L-1对 5 HT量效曲线也有同样的效应 ,pA2值为 6 .5 6。而当剂量为 3× 10 -6、10 -5mol·L-1时 ,对氯化钾 (KCl)量效曲线没有明显影响。在无钙Krebs液中 ,BWYJ 10 -7、 3× 10 -7、 10 -6和10 -5mol·L-1呈浓度依赖性抑制NA所致血管条的短暂收缩 ,对复Ca2 后NA所诱发的持续收缩也呈剂量依赖性抑制作用 ,但其剂量达 10 -5mol·L-1时尚不能抑制咖啡因在无Ca2 液中所致收缩。结论 :BWYJ可能是一种α受体阻断剂 ,兼有拮抗 5 HT受体的作用。其扩血管的机理可能是通过阻断细胞膜上的α受体或 5 HT受体 ,从而抑制这些受体中介的Ca2 内流和Ca2 释放所致。     

阿司匹林铜对离体兔主动脉血管条收缩的影响(英文)

目的:观察阿司匹林铜对离体免胸主动脉血管平滑肌的作用。方法:取免胸主动脉条,观察阿司匹林铜对去甲肾上腺素(NE)、KCl、CaCl_2诱导收缩作用的影响。结果:证实阿司匹林铜和对照物硫酸铜拮抗NE诱导的兔胸主动脉条收缩,IC_(50)分别为31nmol/L和0.29μmol/L,而阿司匹林本身没有拮抗作用。阿司匹林铜对KCl、CaCl_2诱导的收缩没有影响。在去内皮细胞兔胸主动脉条上,观察到相同的作用。结论:阿司匹林铜具有较强的拮抗NE诱导离体兔胸主动脉条收缩的作用,但不能拮抗KCl、CaCl_2诱导的收缩,提示阿司匹林铜通过阻断受体调控钙通道,舒张血管平滑肌。     

Comparative effects of verapamil and sodium nitroprusside on contraction and 45Ca uptake in the smooth muscle of rabbit aorta, rat aorta and guinea-pig taenia coli.

The effects of verapamil and sodium nitroprusside on muscle tension and 45Ca uptake activated in different ways were compared in rabbit aorta, rat aorta and guinea-pig taenia coli. In rabbit aorta, K-induced contraction was specifically inhibited by verapamil and noradrenaline-induced contraction by sodium nitroprusside. In rat aorta, both K-induced and noradrenaline-induced contractions were inhibited by verapamil or by sodium nitroprusside also. In taenia, both K- and histamine-induced sustained contractions were inhibited by verapamil but not by sodium nitroprusside. The effect of verapamil was competitively antagonized by external Ca, while that of sodium nitroprusside was not. High K, noradrenaline and histamine increased the rate of 45Ca uptake in aortae and taenia. In rabbit aorta the increment in response to high K was specifically inhibited by verapamil and the increment induced by noradrenaline was specifically inhibited by sodium nitroprusside. In rat aorta, increments induced by both high K and noradrenaline were inhibited by verapamil and by sodium nitroprusside. In taenia, the increments induced by high K and by histamine were inhibited by verapamil but not by sodium nitroprusside. These results suggest different characteristics of Ca entry systems in these smooth muscles. In rabbit aorta, there seem to be two Ca channels, one of which is activated by high K and inhibited by verapamil, while the other is activated by noradrenaline and inhibited by sodium nitroprusside. In rat aorta, both K- and noradrenaline-activated Ca pathways are sensitive to both verapamil and sodium nitroprusside whereas, in taenia, both K- and histamine-activated Ca pathways are sensitive only to verapamil.     

The inhibitory action of two thrombin inhibitors (TI-189 and TI-233) on the contractile responses to 5-hydroxytryptamine and prostaglandin endoperoxide analogue (U-44069) in isolated vascular strips.

1. Two arginine derivatives that were developed as thrombin inhibitors (TI-189 and TI-233) selectively inhibited the 5-hydroxytryptamine (5-HT)-induced contraction of rabbit aortic strips in a competitive manner. The PA2 values of TI-189 and TI-233 were 5.24 +/- 0.21 and 6.23 +/- 0.32 respectively. 2. Even at 10(-4) M they had no inhibitory effect on the contractile response to noradrenaline (NA), histamine, prostaglandin E2 (PGE2), PGF2 alpha, arachidonic acid or potassium in rabbit aortic strips. 3. In dog basilar and coronary arterial strips and also in rat fundus, both agents inhibited the 5-HT response in a non-competitive manner. 4. At 10(-5) M, TI-233 but not TI-189 antagonized effects of NA and KCl in the dog basilar and coronary arteries. 5. These arginine derivatives decreased the contractile responses induced by a prostaglandin endoperoxide analogue (U-44069) in rabbit aorta and in dog basilar and coronary arteries but there was no evidence for competitive antagonism. 6. These results indicate that the arginine derivatives are competitive antagonists selective for 5-HT receptors in rabbit aorta.     

Mode of action of sodium nitroprusside on vascular smooth muscle

1. Sodium nitroprusside is a potent relaxant of smooth muscles with a predominantly tonic response, e.g. rat aorta contracted by noradrenaline, angiotensin II, Phe2-Lys8-vasopressin, BaC1(2), or KC1, and guinea-pig tracheal smooth muscle contracted by carbachol. 2. Smooth muscle preparations from the splanchnic region and with varying degrees of phasic contractility are less sensitive and develop tachyphylaxis (portal vein, duodenum of the rat) or are unresponsive to sodium nitroprusside (vas deferens, uterus of the rat). 3. Cardiac auricles of the guinea pig are not affected by sodium nitroprusside in either frequency or amplitude or spontaneous contractions. 4. Sdium nitroprusside causes a parallel shift of the dose-response curve of rat aorta to noradrenaline to the right and reduces the maximum response. 5. The drug has no blocking or stimulant effect on alpha- or beta-adrenoceptors, respectively. 6. Sodium nitroprusside inhibits the contractile response of calcium-depleted depolarized rat aorta to extra-cellular calcium. Like verapamil, it inhibits the increment in 45calcium uptake of rabbit aorta elicited by K+. Sodium nitroprusside significantly reduced 45calcium binding by microsomes prepared from rabbit aorta. 7. Rabbit aorta was incubated with lanthanum chloride to prevent calcium influx; sodium nitroprusside reduced the maintained rapid contraction phase in response to noradrenaline which is believed to be based on the intracellular activation of calcium. 8. In rat aorta, cellular cAMP and ATP levels were not found to be affected by the drug. 9. Rabbit aorta, "skinned" by glycerination is unresponsive to sdoium nitroprusside. 10. It is concluded that sodium nitropruside acts on exictation-contraction coupling predominantly in tonic smooth muscle by interfering with both the influx and the intracellular activation of calcium.     

Age-related changes in the sensitivity to verapamil and sodium nitroprusside of vascular smooth muscle of rabbit aorta.

Age-related changes in the sensitivity to verapamil and sodium nitroprusside were examined in isolated aortic strips of the rabbit. In the aortae of newborn rabbits within 10 days of birth, the resting tone of the muscle was strongly reduced by sodium nitroprusside but not by either Ca-deficient solution or by verapamil. High K-induced contraction and noradrenaline-induced contraction were both inhibited by verapamil or sodium nitroprusside. In the aortae of 24 day-old rabbits, resting tension was slightly reduced by sodium nitroprusside but not by verapamil. High K-induced contraction was less sensitive to sodium nitroprusside than to verapamil whereas noradrenaline-induced contraction was less sensitive to verapamil than to sodium nitroprusside. In the aortae isolated from 60 day-old or older rabbits, resting tension was not affected by either sodium nitroprusside or verapamil. High K-induced contraction was inhibited by verapamil whereas sodium nitroprusside showed only a weak inhibitory effect. Noradrenaline-induced contraction was inhibited by sodium nitroprusside although verapamil had only a slight inhibitory effect. In the aortae of 1 day-old and also in adult rabbits, noradrenaline induced an additional increase in muscle tension when applied during the sustained contraction induced by high K. It is suggested that, in the newborn rabbit aorta, the voltage-dependent Ca channel is sensitive to both verapamil and sodium nitroprusside and the sensitivity to sodium nitroprusside gradually decreases during maturation whereas the receptor-linked Ca channel is also sensitive to both of the inhibitors at birth but the sensitivity to verapamil gradually decreases with age.     

乙酰天麻素对血管平滑肌的解痉作用

天麻属兰科植物,近年来从天麻中提出一个有效成分天麻素,经实验及临床观察认为是安全有效的镇静药。对神经衰弱,血管神经性头痛等可使症状减轻或消除。昆明制药厂对天麻素的结构进行了改造,合成了一系列的衍生物,其中乙酰天麻素(acetagastrodine,G2)作用比天麻素强,本文研究乙酰天麻素对血管平滑肌的影响。     

Pilocarpine-induced relaxation of rat tail artery by a non-cholinergic mechanism and in the absence of an intact endothelium.

1. Small strips from third-order branches of rabbit mesenteric artery (approximately 150-200 microM wide) contracted in response to noradrenaline (10 microM) or 5-hydroxytryptamine (5-HT; 10 microM) in oxygenated Krebs solution containing 2.5 mM Ca2+. In a Ca(2+)-free mock intracellular solution (0 Ca2+ plus 0.2 mM EGTA), noradrenaline (10 microM) and caffeine (10 mM) induced only a single, transient contraction in artery strips, while 5-HT (10 microM) failed to induce any response. 2. In strips of mesenteric artery which had been permeabilized with Staphylococcus alpha-toxin and bathed in Ca(2+)-free mock intracellular solution, noradrenaline (10 microM), caffeine (10 mM) and D-myo-inositol (1,4,5)-trisphosphate (IP3, 100 microM), but not 5-HT (10 or 100 microM) induced a transient contraction. In contrast to the non-permeabilized strips, contractions to noradrenaline, caffeine and IP3 were restored by prior incubation (10 min) in solution containing 0.08 microM Ca2+. The contractions to noradrenaline and IP3 in permeabilized muscle strips required the presence of 100 microM guanosine 5'-triphosphate (GTP), although in the absence of Ca2+. GTP alone did not induce contraction. 3. Exposure of permeabilized mesenteric artery strips to IP3 significantly reduced the subsequent contractile responses to caffeine. Contractile responses to caffeine and IP3 were abolished by the Ca(2+)-ATPase inhibitor, thapsigargin (1 microM). 4. Ca2+ (0.1-10 microM) induced concentration-dependent contraction in permeabilized artery strips. In strips which were submaximally contracted with 0.5 microM Ca2+/100 microM GTP, the subsequent addition of 5-HT (10 microM) stimulated further contraction. The protein kinase C inhibitor, H-7 (1 microM) abolished the 5-HT/GTP-induced contraction, but did not alter the contraction to Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects on isolated arteries from rat, rabbit and man of NNC 70-0270, a synthetic atrial natriuretic factor analogue with a prolonged action.

A new analogue of ANF (atrial natriuretic factor), NNC 70-0270, was tested in various isolated artery preparations. In the rabbit aorta and renal artery NNC 70-0270 was compared with atriopeptin III and the relative inhibitory potency against noradrenaline-induced contractions (atriopeptin III = 1) was found to be 5 and 9, respectively. Furthermore the duration of the effect (after washout) was prolonged. In the rat aorta the relative potency was 0.5 and a prolonged effect was also found in this preparation. In the human pulmonary artery alpha-hANF was used as a reference, and contractions were induced with noradrenaline (seven experiments) or potassium chloride (three experiments). The relative (alpha-hANF = 1) inhibitory potencies were 0.8 and 1.3, respectively. A pronounced prolongation of the effect was also found in this preparation.     

Comparative study of postsynaptic alpha-adrenoceptors in aorta obtained from human and other mammalian species.

The alpha-adrenoceptor populations in aortic strips from humans, rats, guinea-pigs and rabbits were investigated in vitro, using specific agonists and antagonists. In rabbit and human preparations the activities of the two agonists tested, noradrenaline and methoxamine, were competitively antagonized by prazosin, whereas in the other animal species prazosin showed a competitive antagonism for methoxamine induced contraction, but an uncompetitive behaviour against noradrenaline. The alpha 2-selective agonists B-HT 920 and detomidine did not elicit any effect on aortic strips up to 10(-3) M. On the basis of these results, alpha 1-receptors seem to represent an homogeneous population in human and rabbit aortae, but not in rat and guinea-pig tissues. On the other hand, the contractile response of noradrenaline and methoxamine on aortic strips from the four animal species examined cannot be ascribed to the activation of postsynaptic alpha 2-receptors. Moreover we present preliminary evidence that rat and guinea-pig aortae do not contain a clear subdivision in alpha 1a- and alpha 1b-receptors.     

Contraction of rat thoracic aorta strips by endothelin-1 in the absence of extracellular Ca2+.

1. Endothelin-1 (ET-1) caused a concentration-dependent contraction of helical strips from rat thoracic aorta in the absence of extracellular Ca2+. The Ca(2+)-depleted muscle strips, prepared by three repeated applications of 10(-2) M caffeine or 10(-6) M noradrenaline in Ca(2+)-free buffer, were contracted by 10(-8) M ET-1 in the same manner as non-treated strips. 2. In the absence of extracellular Ca2+, 10(-7) M phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, induced a small but sustained contraction of the rat thoracic aorta strips within 60 min. Preincubation of the strips with 10(-7) M PMA for 60 min in Ca(2+)-free buffer, did not affect the 10(-8) M ET-1-induced contraction, but decreased the 5 x 10(-8) M phorbol 12,13-dibutyrate (PDB)-, or the 10(-7) M PMA-induced contraction, and potentiated the contraction induced by 10(-8) M urotensin II. Preincubation with 10(-8) M ET-1 (which induced maximum contraction) for 25 min in Ca(2+)-free buffer did not change the subsequent contraction induced by PMA (10(-7) M) or urotensin II (10(-8) M) but gave a somewhat lower maximum tension than in non-treated strips. 3. Calyculin-A, a potent inhibitor of phosphatase, also induced a contraction of the Ca(2+)-depleted muscle strips in Ca(2+)-free buffer. Preincubation of the strips with ET-1 (10(-8) M) or PMA (10(-7) M) decreased the calyculin-A (3 x 10(-8) M)-induced contraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impaired cyclic nucleotide-mediated vasorelaxation may contribute to closure of the human umbilical artery after birth.

1. The mechanical and biochemical effects of agents that relax vascular smooth muscle either through elevation of guanosine 3':5'-cyclic monophosphate (cyclic GMP) or adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels were compared in isolated ring preparations of human umbilical artery and rat aorta. Tone was established by preconstriction with 5-hydroxytryptamine. 2. The endothelium-dependent vasodilator calcium ionophore (A23187) (which stimulates endothelium-derived relaxing factor [EDRF] release and thus acts through soluble guanylyl cyclase), sodium nitroprusside (which stimulates soluble guanylyl cyclase directly), and atrial natriuretic peptide (which stimulates particulate guanylyl cyclase) relaxed rat aorta but not human umbilical artery. 3. Sodium nitroprusside, 10 microM, increased cyclic GMP levels from 10 to 390 pmol mg-1 protein at 2 min in rat aorta, as compared with a slower, relatively attenuated rise from 5 to 116 pmol mg-1 protein after 15 min in human umbilical artery. The rise in cyclic GMP in the umbilical artery was not significantly augmented by the cyclic GMP phosphodiesterase inhibitor, MB22948. Atrial natriuretic peptide increased cyclic GMP levels in rat aorta but not in human umbilical artery. 4. Forskolin, 10 microM, which stimulates both soluble and particulate adenylyl cyclase, maximally relaxed rat aorta and increased cyclic AMP levels from 15 to 379 pmol mg-1 protein at 15 min, but did not significantly relax or increase cyclic AMP levels in human umbilical artery. After preincubation with the cyclic nucleotide phosphodiesterase inhibitor, IBMX, 10 microM forskolin increased cyclic AMP levels to 1365 pmol mg-1 protein at 30 min in human umbilical arteries, but these high levels were not accompanied by mechanical relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)