舒芬太尼对去甲肾上腺素诱发自发性高血压大鼠离体胸主动脉收缩的影响

目的 探讨舒芬太尼对去甲肾上腺素(NE)诱发自发性高血压大鼠离体胸主动脉收缩的影响.方法 雄性自发性高血压大鼠8只,体重250～300 g,每只大鼠取离体胸主动脉血管环4段,采用随机区组设计,随机分为4组(n=8):生理盐水对照组(NS组)、低浓度舒芬太尼组(7×10-11mol/L,S1组)、中浓度舒芬太尼组(2×10-10 mol/L,S2组)和高浓度舒芬太尼组(1×10-9mol/L,S3组).将血管环悬挂于血管张力测量装置,张力稳定后加入60 mmol/L KCl收缩血管环,记录血管环张力.洗脱KCl后分别加入生理盐水及不同浓度的舒芬太尼各100 μl,20 min后依次加入终浓度为10-8、10-7、10-6、10-5mol/L的NE,使血管充分收缩,记录不同NE终浓度下血管环张力,计算血管环收缩幅度.结果 与NS组比较,S1组、S2组、S3组血管环收缩幅度降低(P<0.05或0.01).与S1组比较,S2组、S3组血管环收缩幅度降低(P<0.01).与S2组比较,S3组血管环收缩幅度降低(P<0.05或0.01).结论 舒芬太尼可抑制NE诱发自发性高血压大鼠离体胸主动脉收缩,且与浓度有关.

Abstract：

Objective To investigate the effect of sufentanil on norepinephrine (NE)-induced contraction of thoracic aorta isolated from rats with spontaneous hypertension (SH) .Methods Eight male rats with SH weighing 250-300 g were used in this study. The rats were decapitated and their thoracic aortas were isolated and cut into rings 2-3 mm in length. The aorta rings were suspended for isometric tension recording. The aortic rings obtained from SH rats were divided into 4 groups ( n = 8 each) : control group and 3 sufentanil groups. The contraction of aortic rings in response to NE in the absence (control) and presence of 3 concentrations of sufentanil 7 × 10-11 ,2 × 10-10 and 1 × 10-9 mol/L was recorded. Results The amplitude of NE-induced contraction of thoracic aorta was significantly greater in 3 sufentanil groups than in control group. Sufentanil significantly inhibited the NE-induced aortic contration in proportion to concentration. Conclusion Sufentanil can inhibit NE-induced contraction of thoracic aorta isolated from rats with SH in a concentration-dependent manner.     

山莨菪碱对离体大鼠腹主动脉舒缩张力的作用及其机制

目的 观察山莨菪碱对离体大鼠腹主动脉舒缩张力的作用,探讨其作用机制.方法 采用Wistar大鼠离体腹主动脉环(长4～5 mm的血管)灌流技术,观察山莨菪碱累积浓度(每5 min加入山莨菪碱,使营养液中山莨菪碱浓度分别达3×10-6,10-5,3×10-5,10-4,3×10-4 mol/L)对单剂量苯肾上腺素(PE)(10-5 mol/L)预处理的血管舒张作用的影响,及不同浓度山莨菪碱(10-6,10-5,10-4 mol/L)预孵对累积浓度PE(每5 min加入PE,使营养液中PE浓度分别达10-8,3×10-8,10-7,3×10-7,10-6,3×10-6 mol/L)收缩血管作用的影响,分别运用一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(L-NAME)(100 μmol/L)(对照组加入等容积的蒸馏水)和KATP通道阻断剂格列苯脲(Gly)(100 μmol/L)(两对照组分别加入等容积的蒸馏水及溶剂二甲基亚砜DMSO)处理血管环,观察对山莨菪碱舒张血管的抑制作用.结果 山莨菪碱累积浓度对单剂量PE预收缩内皮完整及去内皮血管环均有舒张作用,最大舒张分别为(78.6±6.9)%和(65.76±11.39)%.程度相似,差异无统计学意义(P＞0.05).不同浓度山莨菪碱预孵对累积浓度PE收缩血管环作用呈浓度依赖性抑制,浓度越大,抑制作用越明显.用阻断剂L-NAME及Gly处理后,L-NAME可阻断山莨菪碱的舒张血管(内皮完整)作用(P＜0.05),而Gly对去内皮血管具阻断作用,但只在2 min时与对照组差异有统计学意义(P＜0.05).结论 山莨菪碱具有内皮及平滑肌依赖性舒张血管作用,即通过内皮上一氧化氮-环鸟苷酸(NO-cGMP)及平滑肌上α受体发挥作用.山莨菪碱抑制血管收缩主要通过ATP依赖性K+通道发挥作用.     

姜酚对家兔胸主动脉平滑肌的舒张作用及其机制

目的 观察姜酚(gingerol)对家兔胸主动脉平滑肌的舒张作用并探讨其作用机制.方法 制备离体内皮完整的和去内皮胸主动脉环肌条,悬挂于恒温浴槽中,并将其与张力-位移换能器相连记录血管环肌条张力的变化,所有标本分为内皮完整组和去内皮组.内皮完整组分为1×10-5 mol/L去甲肾上腺素(NE)+不同浓度gingerol组(1×10-8、1 ×10-7、1 ×10-6、1 ×10-5、1×10-4、1×10-3 mol/L,下同)、20 mmol/L KCl+不同浓度gingerol组、1×10-5 mol/L NE+左旋-硝基精氨酸甲脂(L-NAME)+不同浓度gingerol组、1×10-5 mol/L NE+吲哚美辛+不同浓度gingerol组、20 mmol/LKCl+ L-NAME+不同浓度gingerol组、20 mmol/L KCl+吲哚美辛+不同浓度gingerol组;去内皮组分为1×10-5 mol/L NE+不同浓度gingerol组、20 mmol/L KCl+不同浓度gingerol组.结果 (1)gingerol能抑制1×10-5 mol/L的NE或20 mmol/L的KCl引起的胸主动脉平滑肌收缩并呈剂量依赖性,另外,gingerol对内皮完整的胸主动脉的舒张作用较去内皮的胸主动脉明显增强(P＜0.05).(2)内皮完整的胸主动脉组,L-NAME能显著抑制gingerol对胸主动脉平滑肌的舒张作用(％,NE处理组:94.83±3.63比96.83±1.82、91.17 ±2.89比94.83±2.68、83.83±2.23比94.67±2.73、78.00±3.54比92.33±2.91、67.83±2.37比90.83±3.77、62.83±3.42比89.67±3.15;KCl处理组:90.33±8.33比98.17±7.56、80.83±7.24比96.83±7.28、70.83±7.57比92.17±7.31、67.83±7.68比89.83±7.23、62.83±7.49比90.33±8.87、57.33±8.32比87.67±8.97,P＜0.05).(3)内皮完整的胸主动脉组吲哚美辛能显著抑制gingerol对胸主动脉平滑肌的舒张作用(％,NE处理组:93.83±7.61比97.83±7.45、92.50±10.13比95.33±8.36、86.67±8.24比93.83±7.28、79.83±7.36比89.83±7.63、67.83±7.46比85.33±8.94、61.83 ±7.55比81.83 ±7.25;KC1处理组:90.17±7.77比96.17±7.31、79.67±8.65比91.33±8.62、72.17 ±7.48比85.67±8.76、70.83±7.78比83.17±7.79、56.83±7.62比77.83±7.29、54.17 ±7.68比74.83±7.34,P＜0.05).结论 gingerol对NE和KCl所诱发的收缩具有剂量依赖性的抑制作用,其机制可能与内皮产生的NO和前列环素有关.     

降钙素基因相关肽混合去甲肾上腺素对大鼠心肌细胞L-型钙电流的影响

目的 探讨降钙素基因相关肽(CGRP)混合去甲肾上腺素(NE)对大鼠心肌细胞L-型钙电流(ICa-L)的影响.方法 SD大鼠,雌雄不拘,体重260～280 g,急性分离其心肌细胞,用全细胞膜片钳方法记录ICa-L.采用随机数字表法,将心肌细胞随机分为3组(n=6):CGRP组用含CGRP 1×10-7mol/L的台氏液灌流;NE组用含NE 1×10-6mol/L的台氏液灌流;CGRP+NE组(CN组)用含NE 1×10-6mol/L+CGRP 1×10-7mol/L的台氏液灌流.各组均灌流1 min,流速2 ml/min;然后用台氏液洗脱1 min.于灌流前1 min、灌流1 min和洗脱1 min时,记录ICa-L峰值,并绘制CGRP或NE灌流后ICa-L的电流-电压曲线.结果 CGRP可抑制心肌细胞ICa-L(P<0.05).NE可促进心肌细胞ICa-L(P<0.05).与CN组比较,灌流1 min时CGRP组ICa-L降低,NE组ICa-L升高(P<0.05).CGRP使心肌细胞ICa-L的电流-电压曲线明显上移;NE使心肌细胞ICa-L的电流一电压曲线明显下移.结论 CGRP可削弱NE对大鼠心肌细胞ICa-L的促进作用.

Abstract：

Objective To investigate the effects of calcitonin gene-related peptide (CGRP) combined with norepinephrine (NE) on L-type calcium current (LCa-l) in rat ventricular myocytes. Methods Ventricular myocytes were isolated from SD rats (weighing 260-280 g) by retrograde perfusion of the heart via the aorta with an enzyme-containing solution as previously described. Whole-cell patch-clamp recording was made using Axopatch 200B amplifier. The cells were perfused for 1 min with Tyrode solution containing CGRP 1 × 10-7 mol/L (group CGRP) , NE 1 × 10-6 mol/L (group NE), or CGRP 1 × 10-7 mol/L + NE 1 × 10-6 mol/L (group CN) and again washed with Tyrode solution. ICa-L was recorded 1 min before and 1 min after the cells were perfused and 1 min after the cells were washed. I-V curve of ICa-L was made after the cells were perfused with solution containing CGRP or NE alone. Results CGRP significantly inhibited the peak of ICa-L, while NE significantly promoted the peak of ICa-L(P < 0.05) . The peak of ICa-L was significantly decreased 1 min after the cells were perfused in group CGRP,while increased 1 min after the cells were perfused in group NE compared with group CN ( P < 0.05). CGRP made the I-V curve of ICa-L move up-ward, while NE made the I-V curve of ICa-L move down-ward. Conclusion CGRP can weaken the promotion of ICa-L induced by NE in rat ventricular myocytes.     

舒芬太尼对去甲肾上腺素诱发自发性高血压大鼠离体胸主动脉收缩的影响

Objective To investigate the effect of sufentanil on norepinephrine (NE)-induced contraction of thoracic aorta isolated from rats with spontaneous hypertension (SH) .Methods Eight male rats with SH weighing 250-300 g were used in this study. The rats were decapitated and their thoracic aortas were isolated and cut into rings 2-3 mm in length. The aorta rings were suspended for isometric tension recording. The aortic rings obtained from SH rats were divided into 4 groups ( n = 8 each) : control group and 3 sufentanil groups. The contraction of aortic rings in response to NE in the absence (control) and presence of 3 concentrations of sufentanil 7 × 10-11 ,2 × 10-10 and 1 × 10-9 mol/L was recorded. Results The amplitude of NE-induced contraction of thoracic aorta was significantly greater in 3 sufentanil groups than in control group. Sufentanil significantly inhibited the NE-induced aortic contration in proportion to concentration. Conclusion Sufentanil can inhibit NE-induced contraction of thoracic aorta isolated from rats with SH in a concentration-dependent manner.     

舒芬太尼对去甲肾上腺素诱发自发性高血压大鼠离体胸主动脉收缩的影响

Objective To investigate the effect of sufentanil on norepinephrine (NE)-induced contraction of thoracic aorta isolated from rats with spontaneous hypertension (SH) .Methods Eight male rats with SH weighing 250-300 g were used in this study. The rats were decapitated and their thoracic aortas were isolated and cut into rings 2-3 mm in length. The aorta rings were suspended for isometric tension recording. The aortic rings obtained from SH rats were divided into 4 groups ( n = 8 each) : control group and 3 sufentanil groups. The contraction of aortic rings in response to NE in the absence (control) and presence of 3 concentrations of sufentanil 7 × 10-11 ,2 × 10-10 and 1 × 10-9 mol/L was recorded. Results The amplitude of NE-induced contraction of thoracic aorta was significantly greater in 3 sufentanil groups than in control group. Sufentanil significantly inhibited the NE-induced aortic contration in proportion to concentration. Conclusion Sufentanil can inhibit NE-induced contraction of thoracic aorta isolated from rats with SH in a concentration-dependent manner.     

降钙素基因相关肽混合去甲肾上腺素对大鼠心肌细胞L-型钙电流的影响

Objective To investigate the effects of calcitonin gene-related peptide (CGRP) combined with norepinephrine (NE) on L-type calcium current (LCa-l) in rat ventricular myocytes. Methods Ventricular myocytes were isolated from SD rats (weighing 260-280 g) by retrograde perfusion of the heart via the aorta with an enzyme-containing solution as previously described. Whole-cell patch-clamp recording was made using Axopatch 200B amplifier. The cells were perfused for 1 min with Tyrode solution containing CGRP 1 × 10-7 mol/L (group CGRP) , NE 1 × 10-6 mol/L (group NE), or CGRP 1 × 10-7 mol/L + NE 1 × 10-6 mol/L (group CN) and again washed with Tyrode solution. ICa-L was recorded 1 min before and 1 min after the cells were perfused and 1 min after the cells were washed. I-V curve of ICa-L was made after the cells were perfused with solution containing CGRP or NE alone. Results CGRP significantly inhibited the peak of ICa-L, while NE significantly promoted the peak of ICa-L(P < 0.05) . The peak of ICa-L was significantly decreased 1 min after the cells were perfused in group CGRP,while increased 1 min after the cells were perfused in group NE compared with group CN ( P < 0.05). CGRP made the I-V curve of ICa-L move up-ward, while NE made the I-V curve of ICa-L move down-ward. Conclusion CGRP can weaken the promotion of ICa-L induced by NE in rat ventricular myocytes.     

降钙素基因相关肽混合去甲肾上腺素对大鼠心肌细胞L-型钙电流的影响

Objective To investigate the effects of calcitonin gene-related peptide (CGRP) combined with norepinephrine (NE) on L-type calcium current (LCa-l) in rat ventricular myocytes. Methods Ventricular myocytes were isolated from SD rats (weighing 260-280 g) by retrograde perfusion of the heart via the aorta with an enzyme-containing solution as previously described. Whole-cell patch-clamp recording was made using Axopatch 200B amplifier. The cells were perfused for 1 min with Tyrode solution containing CGRP 1 × 10-7 mol/L (group CGRP) , NE 1 × 10-6 mol/L (group NE), or CGRP 1 × 10-7 mol/L + NE 1 × 10-6 mol/L (group CN) and again washed with Tyrode solution. ICa-L was recorded 1 min before and 1 min after the cells were perfused and 1 min after the cells were washed. I-V curve of ICa-L was made after the cells were perfused with solution containing CGRP or NE alone. Results CGRP significantly inhibited the peak of ICa-L, while NE significantly promoted the peak of ICa-L(P < 0.05) . The peak of ICa-L was significantly decreased 1 min after the cells were perfused in group CGRP,while increased 1 min after the cells were perfused in group NE compared with group CN ( P < 0.05). CGRP made the I-V curve of ICa-L move up-ward, while NE made the I-V curve of ICa-L move down-ward. Conclusion CGRP can weaken the promotion of ICa-L induced by NE in rat ventricular myocytes.     

四氢生物蝶呤对吸烟者大隐静脉桥内皮功能的影响

目的 观察四氢生物蝶呤(BH4)对吸烟者大隐静脉桥内皮功能的影响.方法 取12例吸烟(实验组)及10例不吸烟(对照组)行冠状动脉旁路移植术患者的大隐静脉.在器官槽中观察经重碳酸盐缓冲液(KH液)、含0.1 mol/L N-硝基-L-精氨酸(L-NNA)或含20 μmol/L BH4的KH液浸泡30 min后,苯肾上腺素(1×10-5 mol/L)及不同浓度(1×10-9～1×10-5mol/L)的非受体介导钙离子载体引发的血管舒缩反应.结果　最大收缩强度各组间差异无统计学意义(P＞0.05).最大舒张反应:经KH液浸泡后实验组低于对照组[(29.50±6.22)%比(48.20±7.74)%,P＜0.01];经L-NNA[(24.50±5.72)%比(28.80±5.64)%]或BH4[(46.40±6.32)%比(50.80±6.91)%]浸泡后两组差异无统计学意义(P＞0.05).结论　吸烟损伤大隐静脉桥内皮源性一氧化氮介导的血管舒张功能,BH4有利于此功能的恢复.

Abstract：

Objective To observe the effect of tetrahydrobiopterin ( BH4 ) on endothelium function of the great saphenous vein from smokers. Methods The rings of great saphenous vein were selected from 22 patients with coronary artery bypass grafting, which including smoking (experimental group,n = 12) and non-smoking (control group,n = 10) patients. After incubation in Krebs-Henseleit (KH), KH plus BH4 (20 μ mol/L) or N-nitro-L-arginine ( L-NNA, 0. 1 mol/L), the vasoconstriction and vasodilatation were induced by phenylephrine (1 × 10-5 mol/L) and non-receptor-mediated calcium ionophore (A23187,1 × 10-9-1 × 10 -5 mol/L) separately in an organ chamber. Results The maximum constriction in all groups had no significant difference ( P ＞ 0. 05 ). The maximum relaxation was significantly decreased in experimental group as compared with control group [(29.50 ± 6. 22 ) % vs (48.20 ± 7. 74 ) %, P ＜ 0. 01]after incubation in KH, while there was no significant difference (P ＞ 0. 05 ) after incubation in KH plus L-NNA [(24.50±5.72)% vs (28.8 ±5.64)%] or BH4[(46.40 ±6.32)% vs (50.80±6.91)%].Conclusion Smoking impairs the relaxation function mediated by endothelium-derived nitric oxide in great saphenous, which may be restored by BH4.     

咪达唑仑对大鼠离体主动脉的舒张作用

目的观察咪达唑仑对血管张力的直接影响,并探讨其作用机制.方法采用内皮完整和去内皮的大鼠离体主动脉环,首先观察咪达唑仑在3×10-6,10×10-6,30×10-6,100×10-6mol/L浓度时,对去氧肾上腺素(10-6mol/L)引起收缩的血管环等长张力的影响.然后观察咪达唑仑对经亚甲蓝(10-5mol/L)孵浴处理的内皮完整血管环和分别经过维拉帕米(5×10-6mol/L)和四乙胺(5×10-3mol/L)孵浴处理的去内皮血管环张力的影响.结果以上浓度的咪达唑仑对去内皮和内皮完整血管环均有舒张作用.去内皮血管环的舒张反应低于内皮完整血管环(P＜0.05).用亚甲蓝处理的内皮完整环的舒张反应与未经处理时比较无显著性差异(P＞0.05).四乙胺可增强咪达唑仑对去内皮血管环的舒张作用(P＜0.05).维拉帕米不影响咪达唑仑对去内皮血管环的舒张(P＞0.05).结论咪达唑仑对血管具有内皮依赖性和非内皮依赖性的舒张作用,其内皮依赖性的舒张反应与NO-sGC-cGMP途径无关.     

Remifentanil produces vasorelaxation in isolated rat thoracic aorta strips

BACKGROUND: Remifentanil can cause transient instability in hemodynamic variables. However this change may not be solely the result of autonomic or central nervous system inhibition or of centrally mediated vagal stimulation. In this study, the aim was to examine the direct effects of remifentanil on isolated thoracic aorta strips in vitro. METHODS: Forty-five Wistar rat thoracic aorta rings were isolated, and contraction-relaxation responses were recorded. RESULTS: In aortic rings precontracted with phenylephrine or potassium chloride, remifentanil produced concentration-dependent relaxation in both endothelium-intact and denuded rings (P<0.001). Remifentanil induced significantly greater relaxation in intact rings than in those denuded of endothelium, regardless of whether they were precontracted with phenylephrine hydrochloride or KCl (P<0.001). When the endothelium was present, remifentanil produced greater relaxation in KCl-contracted rings than in PE-contracted rings at lower concentrations (10-9 and 10-8), and similar relaxation at higher concentrations (10-7 and 10-6). However, when the endothelium was removed, relaxation was similar in both solutions, at all concentrations (10-9 to 10-6). In intact rings, pretreatment with L-NO-ARG or indomethacin reduced the degree of remifentanil-induced relaxation. In Ca+ +/- free media, calcium-dependent KCl contractions were inhibited in a dose-dependent manner by remifentanil (P<0.001). CONCLUSION: Remifentanil vasodilates by an endothelium-dependent mechanism, involving prostacyclin and nitric oxide released from the endothelium. Its endothelium-independent vasodilation probably occurs via the suppression of voltage-sensitive Ca++ channels.     

Contributions of nitric oxide,EDHF, and EETs to endothelium-dependent relaxation in renal afferent arterioles

BACKGROUND: Acetylcholine-induced endothelium-dependent relaxation in the renal afferent arteriole has been ascribed to nitric oxide, but the role of endothelium-derived hyperpolarizing factors (EDHFs) and 14,15-epoxyeicosatrienoic acid (14,15-EET) are unclear. METHODS: Single afferent arterioles were dissected from kidney of normal rabbits and microperfused in vitro at 60 mm Hg. Vessels were preconstricted submaximally with norepinephrine (10(-8) mol/L). Relaxation was assessed following cumulative addition of ACh (10(-9) to 10(-4) mol/L) alone, or in the presence of indomethacin (to inhibit cyclooxygenase), Nw-nitro-L-arginine (L-NNA) (to inhibit nitric oxide synthase), methylene blue (to inhibit soluble guanylate cyclase), or a combination of L-NNA + methylene blue. To assess contributions by EDHF, studies were repeated with either apamin + charybdotoxin [to block Ca2+-activated K+ channels (KCa)] or with 40 mmol/L KCl. To asses the role of 14,15-EET, relaxations were evaluated in the presence of its competitive inhibitor 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE). RESULTS: Relaxation by acetylcholine was abolished following endothelial denudation. It was unaffected by indomethacin but was inhibited 54%+/- 5% (P < 0.001) by L-NNA, 57%+/- 5% by methylene blue, and 60%+/- 4% by the combination of L-NNA plus methylene blue. Relaxation was inhibited further by KCl (80%+/- 6%) or by apamin + charybdotoxin (96%+/- 2%). 14,15-EEZE, alone, inhibited acetylcholine-induced relaxation by 29%+/- 3%, and by 80%+/- 5% in the presence of L-NNA. CONCLUSION: Acetylcholine-induced afferent arteriolar relaxation depends strongly on both nitric oxide, acting via soluble guanylate cyclase, and on an EDHF, likely 14,15-EET, acting via KCa.     

不同浓度丙泊酚通过缝隙连接通讯对舒张大鼠肠系膜动脉的影响

目的观察丙泊酚对SD大鼠肠系膜动脉的影响和对肠系膜动脉舒张作用是否与缝隙连接通讯相关。方法应用压力肌动图技术,在急性分离的SD大鼠肠系膜动脉2级血管上,观察1×10-7、3×10-7、1×10-6、3×10-6、1×10-5、3×10-5、1×10-4和3×10-4 mol/L丙泊酚对血管直径的影响,预孵育缝隙连接阻断剂18-β甘草次酸(18β-glycyrrhetinic acid,18β-GA)和2-aminoethoxydiphenylborate(2-APB)后,观察丙泊酚对血管直径的影响。结果给予1×10-7、3×10-7、1×10-6、3×10-6、1×10-5、3×10-5、1×10-4和3×10-4 mol/L的丙泊酚,使SD大鼠血管直径从(208.6±13.4)μm分别增加至(213.5±13.6)、(219.7±13.2)、(226.4±12.5)、(234.9±12.3)、(245.5±13.0)、(267.4±15.2)、(336.2±18.3)和(385.9±14.2)μm,1×10-4 mol/L的丙泊酚引起血管直径随着丙泊酚浓度增大而增加(P0.01)。分别预孵育18β-GA和2-APB后,1×10-4 mol/L的丙泊酚对大鼠肠系膜动脉舒张作用明显减弱(P0.01)。结论丙泊酚呈浓度依赖性舒张肠系膜动脉,其作用机制可能与缝隙连接通讯相关。     

Matrix metalloproteinase 2-induced venous dilation via hyperpolarization and activation of K+ channels: relevance to varicose vein formation

BACKGROUND: Varicose veins are a common disorder of extensive venous dilation and remodeling with an as-yet unclear mechanism. Studies have shown increased plasma and tissue levels of matrix metalloproteinases (MMPs) in human varicose veins and animal models of venous hypertension. Although the effects of MMPs are generally attributed to extracellular matrix degradation, their effects on the mechanisms of venous contraction/relaxation are unclear. Our preliminary experiments have demonstrated that MMP-2 causes inhibition of phenylephrine-induced venous contraction. The purpose of this study was to determine whether MMP-induced inhibition of venous contraction involves an endothelium-dependent and/or -independent pathway. METHODS: Circular segments of the inferior vena cava (IVC) were isolated from male Sprague-Dawley rats and suspended between two wire hooks in a tissue bath, and the effects of MMP-2 on phenylephrine- and KCl-induced contraction were measured. To study the role of endothelium-derived vasodilators, experiments were performed in the presence and absence of endothelium; N(G)-l-nitro-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis; indomethacin, an inhibitor of prostacyclin synthesis; cromakalim, an activator of adenosine triphosphate-sensitive K+ channels (K(ATP)); and iberiotoxin, a blocker of large-conductance Ca2+-dependent K+ channels (BK(Ca)) and smooth muscle hyperpolarization. RESULTS: In endothelium-intact IVC segments, phenylephrine (10(-5) mol/L) caused significant contraction that slowly declined to 82.0% in 30 minutes. The addition of MMP-2 (1 microg/mL) caused a gradual decrease of phenylephrine contraction to 39.5% at 30 minutes. In endothelium-denuded IVC, MMP-2 induced a greater reduction of phenylephrine contraction, to 7.6%. In the presence of L-NAME (10(-4) mol/L), MMP-2 caused a marked decrease in phenylephrine contraction, to 4.4%. Large MMP-2-induced inhibition of phenylephrine contraction was also observed in IVC treated with L-NAME plus indomethacin. MMP-2 caused relaxation of phenylephrine contraction in IVC pretreated with cromakalim (10(-7) mol/L), an activator of K(ATP) channels. MMP-2-induced inhibition of phenylephrine contraction was abrogated in the presence of iberiotoxin (10(-8) mol/L), a blocker of BK(Ca). MMP-2 did not inhibit venous contraction during membrane depolarization by 96 mmol/L KCl, a condition that prevents outward K+ conductance and cell hyperpolarization. CONCLUSIONS: MMP-2 causes significant IVC relaxation that is potentiated in the absence of endothelium or during blockade of endothelium-mediated nitric oxide and prostacyclin synthesis. The lack of effects of MMP-2 on KCl contraction and in iberiotoxin-treated veins suggests MMP-2-induced smooth muscle hyperpolarization and activation of BK(Ca) channels--a novel effect of MMP that may play a role in the early stages of venous dilation and varicose vein formation.     

Hirudin (desulfated, 54-65) contracts canine coronary arteries: extracellular calcium influx mediates hirudin-induced contractions

OBJECTIVE: Although the anticoagulatory properties of hirudin are well known, its direct vasoactive effects have not been investigated extensively. Hirudin stimulates nitric oxide and prostacyclin production in noncoronary vascular beds, but its actions on coronary arteries are unknown. MATERIALS AND METHODS: Five-millimeter segments of canine left circumflex coronary arteries were obtained for organ chamber experiments. Some segments were denuded of endothelium before study. Segments were exposed to hirudin (10(-10)-10(-6) mol/L) following precontraction with prostaglandin F(2alpha) with or without pretreatment with indomethacin or calcium channel blockers (verapamil and nifedipine). RESULTS: Hirudin stimulated endothelium-independent contraction in coronary arterial segments. Maximum tension (hirudin 10(-6) mol/L) above precontraction baseline was 33.6 +/- 9.0% (n = 10, P < 0.05) for endothelium-intact and 31.8 +/- 11.5% (n = 8, P < 0.05) for endothelium-denuded arterial segments. Differences between endothelium-intact and endothelium-denuded segments were not significant. Contractile responses to hirudin were unaffected by the presence of indomethacin. Pretreatment with either verapamil or nifedipine (10(-4) mol/L) for 1 h attenuated these contractions. The maximal increase in tension above baseline (hirudin 10(-6) mol/L) for verapamil and nifedipine was only 6.2 +/- 12.4 and 3.8 +/- 7.0% (n = 6, P < 0.05 versus endothelium-intact control), respectively. CONCLUSIONS: Hirudin stimulates endothelium-independent contractions of canine coronary arteries in vitro. Pretreatment with calcium channel blockers attenuates this response, suggesting that extracellular influx of calcium has an important mechanistic role in hirudin-mediated coronary artery constriction.     

Role of endothelium in the modulation of isoflurane-induced vasodilatation in rat thoracic aorta

The mechanisms by which endothelium attenuates vasodilation caused by isoflurane are not well understood. We examined the role of endothelium- derived substances, nitric oxide (NO), endothelium-derived hyperpolarizing factors (EDHF), prostanoids and endothelins in the response to isoflurane in rat thoracic aorta. Increasing cumulative concentrations of isoflurane were administered to aortic rings suspended in Hepes solution and preconstricted with either phenylephrine 10(-6) mol litre-1 or KCl 40 mmol litre-1 (which inhibit EDHF). Rings were intact, denuded or incubated with an inhibitor of nitric oxide synthesis (N omega-nitro-L-arginine (LNNA 5 x 10(-5) mol litre-1), an inhibitor of prostanoid synthesis (indomethacin 10(-5) mol litre-1) or a blocker of the vascular receptors to endothelins (cyclo (- D-trp-D-Asp-Pro-D-Val-Leu (BQ 123 10(-5) mol litre-1)- Endothelium attenuated isoflurane-induced vasodilation in KCl-constricted rings at concentrations of 4% (mean 95 (SEM 4)% vs 72 (4)%; P = 0.0005) and 5% (100 (4)% vs 80 (4)%; P = 0.0008) and in phenylephrine constricted rings at concentrations of 4% (54 (8)% vs 35 (3)%; P = 0.04) and 5% (78 (10)% vs 49 (5)%; P = 0.03). Relaxation was significantly greater in rings treated with LNNA than in intact rings at concentrations of 4% (85 (4)% vs 72 (4)%; P = 0.0005) and 5% (90 (4)% vs 80 (4)%; P = 0.0008). Indomethacin and BQ 123 did not alter isoflurane-induced vasodilation. We conclude that endothelium attenuated the vasodilator effect of isoflurane by a mechanism which was abolished by inhibition of nitric oxide. We hypothesize that isoflurane inhibits the release of nitric oxide, leading to a relative vasoconstriction counter-balancing its vasodilator effect. In contrast, EDHF, prostanoids and endothelins were not involved in the attenuation of isoflurane-induced vasodilatation.