粉防己碱对新西兰白兔阴茎海绵体平滑肌细胞内游离钙离子浓度的影响

目的探讨粉防己碱(Tet)松弛阴茎海绵体平滑肌的作用机制。方法体外培养的第3～4代新西兰白兔阴茎海绵体平滑肌细胞,经钙荧光指示剂Fluo-2/AM负载后,用荧光离子数字成像系统观察Tet对平滑肌细胞内[Ca~(2 )]i的影响。结果Tet对平滑肌细胞内静息[Ca~(2 )]i无明显影响(P>0.05)。在细胞外钙浓度为2.5 mmol/L时,1、10和100μmol/LTet对高钾和去氧肾上腺素(PE)引起的细胞内[ca~(2 )]i升高有浓度依赖性地抑制作用。对40 mmol/L KCl引起的细胞内[Ca~(2 )]i升高的抑制率分别为22.0%、41.0%和73.0%(P<0.05)。对10μmol/L PE引起的细胞内[ca~(2 )]i升高的抑制率分别为15.0%、26.4%和46.6%(P<0.05)。在无细胞外钙时,1μmol/L和10μmol/L Tet对PE引起的细胞内[Ca~(2 )]i升高,无明显影响(P>0.05);而100μmol/L Tet能明显抑制PE引起的细胞内[ca~(2 )]i升高,抑制率为28.2%(P<0.05)。结论Tet可能通过阻滞电压依赖性钙通道、α1受体依赖性钙通道和抑制细胞内钙库释放,降低阴茎海绵体平滑肌细胞内[Ca~(2 )]i水平,这是Tet松弛阴茎海绵体平滑肌的作用机制之一。     

粉防己碱(Tet)对兔子阴茎海绵体平滑肌细胞质中自由钙离子浓度的影响(英文)

目的:探讨粉防己碱(tetrandrine,Tet)松弛阴茎海绵体平滑肌的作用机制。方法:体外培养新西兰白兔阴茎海绵体平滑肌细胞,经钙荧光指示剂 Fluo-2/AM 负载后,用荧光离子数字成像系统观察 Tet 对平滑肌细胞内[Ca~(2 )]_i 的影响。结果:Tet(1,10,100μmol/L)对平滑肌细胞内静息[Ca~(2 )]_i无明显影响(P>0.05)。当细胞外钙离子浓度为2.5 mmol/L 时,Tet(1μmol/L,10 μmol/L,100 μmol/L)抑制了高钾和去氧肾上腺素(PE)导致的细胞内[Ca~(2 )]_i 升高(P<0.05),这种抑制作用具有浓度依赖性。在无细胞外钙时,1 μmol/L和10μmol/L Tet 对 PE 引起的细胞内[Ca~(2 )]_i 升高无明显影响(P>0.05);而100 μmol/L Tet 能明显抑制 PE 引起的细胞内[Ca~(2 )]_i 升高(P<0.05)。结论:Tet 通过阻滞电压依赖性钙通道、α_1受体依赖性钙通道和抑制细胞内钙库释放,降低阴茎海绵体平滑肌细胞内[Ca~(2 )]_i 水平,这是 Tet 松弛阴茎海绵体平滑肌的作用机制之一。     

山莨菪碱对急性肾缺血—再灌注损伤的保护机制

目的:观察山莨菪碱(645-2)对急性肾缺血-再灌注损伤的保护机制.方法:用新西兰大白兔制作急性肾缺血及再灌注损伤动物模型、观察肾组织细胞内游离钙(Ca~(?)i)、第二信使三磷酸肌醇(IP_3)含量的浓度变化及再灌注前2分钟给于654-2后肾组织细胞内Ca~(?)i、IP_3含量的浓度变化.结果:缺血60分钟及再灌注60分钟.肾组织细胞内游离钙及IP_3明显增高,而给于654-2后,肾组织细胞内Ca~(?)i及第二信使三磷酸肌醇(IP_3)的含量明显下降.结论:642—2能减轻急性肾缺血-再灌注损伤时细胞内钙超载.其保护肾组织细胞的作用与细胞内IP_3的降低有密切关系.     

粉防己碱舒张离体新西兰白兔阴茎海绵体平滑肌的机制研究

目的观察粉防己碱(tetrandrine,Tet)对阴茎海绵体平滑肌胞内钙释放和胞外钙内流的影响,初步探讨其舒张作用的机制。方法采用离体阴茎海绵体平滑肌肌条张力记录法,观察Tet对去氧肾上腺素(phenylephrine,PE)和氯化钾(KCI)诱导收缩的肌条的影响；采用无Ca~(2 )-复Ca~(2 )实验法,观察Tet对PE诱导的依赖细胞内钙和细胞外钙的肌条收缩反应的影响。结果Tet对PE或kcl诱导的肌条收缩均具有浓度依赖性的抑制作用。100μmol/L Tet可抑制20μmol/L PE引起的依赖细胞内钙和细胞外钙的肌条收缩(P＜0．05)；结论Tet可通过阻滞电压依赖性钙通道、受体依赖性钙通道和抑制细胞内钙库释放,从而介导其对海绵体平滑肌的舒张作用。     

异丙酚对哮喘豚鼠离体气管平滑肌张力的作用

目的 探讨异丙酚对哮喘豚鼠离体气管平滑肌张力的作用及其作用机制。方法 48只健康豚鼠随机分为哮喘组(n=28)和正常组(n=20),卵蛋白致敏法建立哮喘豚鼠模型,每只豚鼠制备5-7个气管平滑肌环,依据悬挂平滑肌环的营养液中处理因素不同将气管平滑肌环随机分为control亚组、10％Intralipid亚组、10、30、100、300μmol/L Propofol亚组,通过与气管环相连的力-位移换能器记录其张力变化,采用悬挂平滑肌环的营养液中无Ca2+的方法测定异丙酚对Ryanodine受体介导的细胞内Ca2+释放的影响。结果 (1)100μmol/L异丙酚显著舒张哮喘豚鼠静息气管平滑肌。四种浓度异丙酚对乙酰胆碱所致气管平滑肌收缩呈剂量依赖的舒张作用。(2)四种浓度异丙酚预适应可剂量依赖性抑制乙酰胆碱所致气管平滑肌收缩。哮喘组30μmol/L异丙酚预适应使乙酰胆碱所致的气管平滑肌依内钙性收缩由(37.7±2.8)％降为(27.7±1.9)％,依外钙性收缩由(62.3±4.5)％降为(51.5±3.5)％,与control亚组比较差异有显著性(P<0.01)。(3)四种浓度异丙酚抑制乙酰胆碱所致气管平滑肌依内钙性收缩作用,与无Ryanodine作用组比较,差异无显著性(P>0.05)。结论临床相关浓度异丙酚预适应显著抑制乙酰胆碱收缩哮喘豚鼠离体气管平滑肌的作用,其作用机制与Rvanodine受体介导     

异丙酚对中性粒细胞活性氧生成及细胞内游离Ca~(2 )浓度的影响

目的 :测定异丙酚对中性粒细胞 (PMN)激活后活性氧生成以及细胞内游离Ca2 浓度 ([Ca2 ]i)的影响 ,探讨异丙酚影响PMN呼吸爆发的内在机制。方法 :利用电子自旋共振 (ESR)技术和自旋捕捉法 ,观察异丙酚对PMN呼吸爆发产生氧自由基 (ROS)的抑制作用 ;同时采用钙荧光指示剂 (Fura 2 /AM)负载离体PMN并行双波长模式测定不同浓度异丙酚对静息和激活状态下PMN细胞内 [Ca2 ]i 的影响。结果 :高浓度 (75 μM)异丙酚可使静息状态下PMN细胞内 [Ca2 ]i升高 ;在有钙基质中 ,异丙酚对趋化三肽 (fMLP)诱发的PMN胞内 [Ca2 ]i 的升高有明显的降调作用 ,而在无钙基质中则不明显。在无钙基质中 ,高浓度 (≥ 5 0 μM )的异丙酚对fMLP诱发PMN呼吸爆发产生ROS有明显的抑制作用 ;而存在胞外钙浓度时 ,2 5 μM异丙酚的抑制程度更为明显。结论 :异丙酚可通过作用于胞外钙内流和胞内储存钙释放影响静息及激活状态下PMN胞内 [Ca2 ]i;异丙酚在有钙基质中对PMN呼吸爆发产生ROS的抑制作用更为明显 ,提示异丙酚影响PMN胞内 [Ca2 ]i,特别是对胞外钙内流的抑制作用 ,可能是其抑制PMN呼吸爆发的内在机制之一。     

异搏定对胰腺腺泡细胞内游离钙离子浓度的影响

目的:探讨细胞内钙超负荷在急性胰腺炎(AP)发生发展中的作用.方法:使用140只SD大白鼠胆胰管逆行加压注射4.5%牛磺胆酸钠制成AP模型,用荧光指示剂Fura-2/Am测定游离胰腺腺泡细胞内游离钙离子浓度([Ca~(2 )]i).结果:注射后2小时和3小时胰腺呈急性出血坏死性炎症早期改变,制AP模型后AP组[Ca~(2 )]i较对照组明显增高(P<0.001),AP组胰腺腺泡细胞内[Ca~(2 )]i增高值与胰腺病理变化程度呈正相关关系(r_s=0.9727,P<0.001),异搏定治疗可明显提高病鼠生存率和改善胰腺组织出血坏死程度和腺泡细胞超微结构损害.结论:胰腺腺泡细胞内钙超负荷在胆汁性急性水肿性胰腺炎向出血坏死性胰腺炎转变中起明显作用,钙通道阻滞剂异搏定可明显阻止胰腺细胞内钙离子超负荷,是其治疗急性胰腺炎的主要机理之一.     

异丙酚对兔离体气管平滑肌细胞内游离钙离子浓度的影响

目的 评价异丙酚对兔离体气管平滑肌细胞内游离钙离子浓度([Ca2+]i)的影响.方法 采用急性酶分离方法分离兔气管平滑肌细胞,采用随机数字表法,将细胞随机分为3组(n=5):异丙酚组(Ⅰ组,终浓度300 μmol/L)、异丙酚(终浓度300 μmol/L)+2-氨乙基硼酸二苯酯(终浓度40μmol/L)(Ⅱ组)和异丙酚(300 μmol/L)+斯里兰卡肉桂碱(终浓度10 μmol/L)(Ⅲ组).Ⅰ组加入终浓度300 μmol/L的异丙酚,孵育15 min后,用无钙的Hank平衡盐溶液冲洗3次,加入1μmol/L乙酰胆碱,记录[Ca2+]i.Ⅱ组加入终浓度40μmol/L的2-氨乙基硼酸二苯酯孵育15 min后,再加入终浓度为300μmol/L的异丙酚,与2-氨乙基硼酸二苯酯共同孵育15 min后,用无钙的Hank平衡盐溶液冲洗3次,加入1 μmol/L的乙酰胆碱.Ⅲ组加入终浓度10 μmol/L的斯里兰卡肉桂碱孵育15 min后,再加入终浓度为300μmol/L的异丙酚,与斯里兰卡肉桂碱共同孵育15 min后,用无钙的Hank平衡盐溶液冲洗3次,再加入1 μmol/L的乙酰胆碱.通过负荷钙离子荧光指示剂Fluo-3/AM测定气管平滑肌细胞内[Ca2+]i.结果 与Ⅰ组比较,Ⅱ组气管平滑肌细胞内[Ca2+]i差异无统计学意义(P＞0.05),Ⅲ组[Ca2+]i明显降低(P＜0.05).结论 异丙酚可降低兔离体气管平滑肌细胞内[Ca2+]i,其机制可能与抑制内质网1,4,5-三磷酸肌醇通路有关,而与内质网兰诺定通路无关.     

川芎嗪对离体兔阴茎海绵体平滑肌条收缩的影响

目的 初步探讨川芎嗪(Ligustrazine)对离体兔阴茎海绵体平滑肌条的舒张作用及其机制。方法 离体家兔阴茎海绵体平滑肌实验方法,观察川芎嗪对阴茎海绵体平滑肌的舒张效应,测定去氧肾上腺素(PE)和氯化钾(Ka)的浓度-效应曲线。结果 川芎嗪浓度依赖性地舒张PE诱发的阴茎海绵体平滑肌收缩作用,最大舒张效应为(74.1±6.2)％[对照组为(21.9±5.6)％,P<0.01]。不同浓度的川芎嗪可使PE和KCL的浓度-效应曲线右移,最大收缩反应降低,高浓度(0.8g/L)时抑制收缩作用更显著。结论 川芎嗪有明显的舒张阴茎海绵体平滑肌作用,并呈剂量依赖性。川芎嗪舒张阴茎海绵体平滑肌机制可能与抑制细胞外钙内流有关。     

甲状旁腺素、血小板胞浆游离钙在尿毒症患者血压调节中的作用

目的 了解血透患者甲状旁腺素[PTH(1～84)]和血小板胞内游离钙浓度{pt[Ca~(2 )]i}在血压调节中的作用。方法 用Fura-2荧光测定法和免疫放射法对24例血透患者测定上述两项内容。结果 HD患者的静息pt[Ca~(2 )]i和PTH(1～84)是升高的,高血压者升高更为明显。静息pt[Ca~(2 )]i与PTH(1～84)相关。多因素逐步回归显示PTH(1～84)、pt[Ca~(2 )]i为影响HD患者平均动脉压的主要因素。结论 PTH(1～84)、pt[Ca~(2 )]i可能是主要影响尿毒症患者血压的因素。     

Mechanisms of direct inhibitory action of propofol on uterine smooth muscle contraction in pregnant rats.

BACKGROUND: Although propofol directly inhibits uterine smooth muscle contraction, the mechanisms of this effect are still unknown. The current study aimed to clarify the mechanisms of the inhibitory effect of propofol on oxytocin-induced uterine smooth muscle contraction by measuring (1) the concentration of intracellular free Ca(2+) ([Ca(2+)](i)) simultaneously with muscle tension, (2) the amount of intracellular inositol 1,4,5-triphosphate ([IP(3)](i)), and (3) voltage-dependent Ca(2+) channel (VDCC) activity. METHODS: Uterine smooth muscle tissues were obtained from pregnant rats (in late gestation). [Ca(2+)](i) with isometric tension was monitored by the 500-nm light emission ratio of preloaded Ca(2+) indicator fura-2. [IP(3)](i) and VDCC activity were measured by radioimmunoassay and patch clamp techniques, respectively. The uterine smooth muscle was stimulated by 20 nm oxytocin and exposed to propofol (10(-7) approximately 10(-4) m). RESULTS: Propofol had significant inhibitory effects on oxytocin-induced uterine smooth muscle contraction and increased [Ca(2+)](i) in pregnant rats in a dose-dependent manner, without affecting the agonist-receptor binding affinity. Propofol inhibited the increase in [IP(3)](i) induced by oxytocin. Propofol also inhibited VDCC activity in both activated and inactivated states. The solvent Intralipid had no effects on these parameters. CONCLUSIONS: Propofol inhibits oxytocin-induced uterine smooth muscle contraction, at least in part, by decreasing [Ca(2+)](i) without affecting agonist-receptor binding; the inhibitory effect of propofol on [Ca(2+)](i) might be mediated both by a decrease in [IP(3)](i) and by inhibition of VDCC activity.     

Mechanisms of Direct Inhibitory Action of Propofol on Uterine Smooth Muscle Contraction in Pregnant Rats

Background : Although propofol directly inhibits uterine smooth muscle contraction, the mechanisms of this effect are still unknown. The current study aimed to clarify the mechanisms of the inhibitory effect of propofol on oxytocin-induced uterine smooth muscle contraction by measuring (1) the concentration of intracellular free Ca2+ ([Ca2+]i) simultaneously with muscle tension, (2) the amount of intracellular inositol 1,4,5-triphosphate ([IP3]i), and (3) voltage-dependent Ca2+ channel (VDCC) activity.

Methods : Uterine smooth muscle tissues were obtained from pregnant rats (in late gestation). [Ca2+]i with isometric tension was monitored by the 500-nm light emission ratio of preloaded Ca2+ indicator fura-2. [IP3]i and VDCC activity were measured by radioimmunoassay and patch clamp techniques, respectively. The uterine smooth muscle was stimulated by 20 nm oxytocin and exposed to propofol (10-7 ~ 10-4 m).

Results : Propofol had significant inhibitory effects on oxytocin-induced uterine smooth muscle contraction and increased [Ca2+]i in pregnant rats in a dose-dependent manner, without affecting the agonist-receptor binding affinity. Propofol inhibited the increase in [IP3]i induced by oxytocin. Propofol also inhibited VDCC activity in both activated and inactivated states. The solvent Intralipid(R) had no effects on these parameters.     

Mechanisms Underlying the Inhibitory Effect of Propofol on the Contraction of Canine Airway Smooth Muscle

Background: Propofol has been shown to produce relaxation of preconstricted airway smooth muscle. Although the inhibition of calcium mobilization is supposed to be the major mechanism of action, the whole picture of the mechanisms is not completely clear.

Methods: Contractile response was performed using canine tracheal rings. The effects of propofol on carbachol-induced mobilization of intracellular Ca2+ and phosphoinositide hydrolysis were measured using cultured canine tracheal smooth muscle cells by monitoring fura-2 signal and assessing the accumulation of [3H]-inositol phosphates. To detect the effect of propofol on muscarinic receptor density and affinity, [3H]N-methyl-scopolamine was used as a radioligand for receptor binding assay.

Results: Pretreatment with propofol shifts the concentration-response curves of carbachol-induced smooth muscle contraction to the right in a concentration-dependent manner without changing the maximal response. Propofol not only decreased the release of Ca2+ from internal stores but also inhibited the calcium influx induced by carbachol. In addition, carbachol-induced inositol phosphate accumulation was attenuated by propofol; the inhibitory pattern was similar to the contractile response. Moreover, propofol did not alter the density of muscarinic receptors. The dissociation constant value was not altered by pretreatment with 100 [mu]M propofol but was significantly increased by 300 [mu]M (propofol, 952 +/- 229 pM; control, 588 +/- 98 pM; P < 0.05).     

Mechanisms underlying the inhibitory effect of propofol on the contraction of canine airway smooth muscle.

BACKGROUND: Propofol has been shown to produce relaxation of preconstricted airway smooth muscle. Although the inhibition of calcium mobilization is supposed to be the major mechanism of action, the whole picture of the mechanisms is not completely clear. METHODS: Contractile response was performed using canine tracheal rings. The effects of propofol on carbachol-induced mobilization of intracellular Ca2+ and phosphoinositide hydrolysis were measured using cultured canine tracheal smooth muscle cells by monitoring fura-2 signal and assessing the accumulation of [3H]-inositol phosphates. To detect the effect of propofol on muscarinic receptor density and affinity, [3H]N-methyl-scopolamine was used as a radioligand for receptor binding assay. RESULTS: Pretreatment with propofol shifts the concentration-response curves of carbachol-induced smooth muscle contraction to the right in a concentration-dependent manner without changing the maximal response. Propofol not only decreased the release of Ca2+ from internal stores but also inhibited the calcium influx induced by carbachol. In addition, carbachol-induced inositol phosphate accumulation was attenuated by propofol; the inhibitory pattern was similar to the contractile response. Moreover, propofol did not alter the density of muscarinic receptors. The dissociation constant value was not altered by pretreatment with 100 microM propofol but was significantly increased by 300 microM (propofol, 952+/-229 pM; control, 588+/-98 pM; P<0.05). CONCLUSIONS: Propofol attenuates the muscarinic receptor-mediated airway muscle contraction. The mechanism underlying these effects was attenuation of inositol phosphate generation and inhibition of Ca2+ mobilization through the inhibition of the receptor-coupled signal-transduction pathway.     

The effect of propofol on angiotensin II-induced Ca(2+) mobilization in aortic smooth muscle cells from normotensive and hypertensive rats

We studied the effect of propofol (5.6-560 micromol/L; 1-100 microg/mL) on the mechanisms involved in Ca(2+) mobilization elicited by angiotensin II (AngII) in Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats. We studied the variations in intracellular Ca(2+) ([Ca(2+)](i)) concentrations in cultured aortic vascular smooth muscle cells (VSMCs) isolated from 6-wk-old WKY and SHR rats loaded with the Ca(2+)-sensitive fluorescent dye, Fura-2, using fluorescent imaging microscopy. In the absence of external Ca(2+), AngII (1 micromol/L) induced a transient [Ca(2+)](i) mobilization from internal stores that was larger in SHR than in WKY rats. Ca(2+) influx was assessed after external Ca(2+) (1 mmol/L) reintroduction. Propofol (1-100 microg/mL) added 5 min before the experiments did not alter AngII-induced Ca(2+) release from internal stores in either strain. By contrast, Ca(2+) influx elicited by AngII was significantly decreased by propofol. This effect occurred at a smaller concentration of propofol in the SHR than in the WKY rats. When Ca(2+) stores were depleted by exposure of cells to thapsigargin, an inhibitor of the sarcoendoplasmic reticulum Ca(2+)-ATPase, reintroduction of Ca(2+) to the medium induced a capacitative Ca(2+) influx of similar magnitude than that elicited by AngII. This influx was also significantly decreased by propofol at 100 microg/mL ( WKY: 27 +/- 3% of control values, n = 107; SHR: 16 +/- 3%, n = 47; P < 0.001). In conclusion, propofol decreased AngII-induced Ca(2+) influx through voltage-independent channels, without altering Ca(2+) release from internal stores in aortic VSMCs. The hypertensive rats were found to be more sensitive to the effect of propofol than the normotensive rats. This suggests that the response of VSMCs to AngII may be altered by propofol. IMPLICATIONS: In rat aortic vascular smooth muscle cells, propofol reduced angiotensin II-elicited Ca(2+) entry through capacitative Ca(2+) channels without altering Ca(2+) release from intracellular stores. Spontaneously hypertensive rats were more sensitive to these effects of propofol than normotensive rats. The response of vascular smooth muscle cells to angiotensin II may be altered by propofol.     

Effects of propofol on guinea pig respiratory smooth muscle

The effects of propofol on the tone of guinea pig respiratory smooth muscle was studied both in vitro and in vivo. In vitro, the activity of propofol on tracheal smooth muscle was investigated using a force displacement transducer for isometric tension responses. Isoproterenol was used as the control. Concentration-response curves to propofol and isoproterenol were obtained using a cumulative dose schedule. Propofol (0.32–10.24 μg·ml⁻¹) relaxed the tracheal smooth muscle in a concentration-dependent manner, but was less potent than isoproterenol (equipotent molar ratio 29 000∶1). This effect of propofol was not affected by prior administration of atropine, propranolol, prazocin, or yohimbine, and it did not appear to be mediated via calcium antagonism. The solvent for propofol (10% intralipid) had no effect on the tracheal smooth muscle in vitro. The in vivo study measured the effect of propofol on lung pressure in deeply anesthetized guinea pigs using histamine induced bronchoconstriction. Propofol (1–4.5 mg·kg⁻¹, i.v.) exhibited neither relaxant nor constrictor effects. It is possible that the effects of propofol observed in vitro are due to nonspecific action, while the finding of no effect in vivo could be due to different tissue sensitivity to propofol, i.e., tracheal smooth muscle may be more responsive than bronchial smooth muscle. Propofol does not seem to have any deleterious effects on airway smooth muscle.     

Propofol inhibits phorbol 12, 13-dibutyrate-induced, protein kinase C-mediated contraction of rat aortic smooth muscle

BACKGROUND: Propofol induces dose-dependent vasodilation and hypotension in the clinical situation, and protein kinase C (PKC)-mediated Ca2+ sensitization plays an important role in vascular smooth muscle contraction. This study is designed to examine the effects of propofol on the active phorbol ester (phorbol 12, 13-dibutyrate; PDBu)-induced, PKC-mediated contraction of rat aortic smooth muscle. METHODS: The PDBu-induced contraction of endothelium-denuded rat aortic rings was measured in the presence or absence of PKC inhibitor, bisindolylmaleimide I, or propofol, using isometric force transducers. The PDBu-induced PKC phosphorylation of endothelium-denuded rat aortic strips was detected in the presence or absence of bisindolylmaleimide I or propofol, using Western blotting. RESULTS: PDBu, but not the inactive phorbol ester, 4-alpha-phorbol 12-myristate-13-acetate, dose-dependently induced both a slowly developing sustained contraction and PKC phosphorylation of rat aortic smooth muscle, reaching the peak level at the concentration of 10(-6) M. The PDBu (10(-6) M)-induced contraction was dose-dependently inhibited by bisindolylmaleimide I with reductions of 6.8 +/- 1.8% (P > 0.05), 39.8 +/- 8.7% (P < 0.01) and 96.7 +/- 1.4% (P < 0.01) in response to concentrations of 5 x 10(-7) M, 10(-6)x M and 5 x 10(-6) M, respectively, and by propofol with decreases of 5.2 +/- 1. 6% (P > 0.05), 9.4 +/- 1.7% (P < 0.05), 65.3 +/- 9.2% (P < 0.01) and 96.2 +/- 1.6% (P < 0.01) in response to concentrations of 5 x 10(-7) M, 10(-6) M, 5 x 10(-6) M and 10(-5) M, respectively. Both bisindolylmaleimide I and propofol also inhibited the PDBu-induced increase in the density of the phosphorylated PKC bands in a dose-dependent manner, with decreases of 6.3 +/- 2.8% (P > 0.05), 42.9 +/- 3.2% (P < 0.01) and 96.6 +/- 3.4% (P < 0.01) in response to 5 x 10(-7) M, 10(-6) M or 5 x 10(-6) M bisindolylmaleimide I, respectively, and with decreases of 4.2 +/- 2.5% (P > 0.05), 13.5 +/- 1.7% (P < 0.05), 69.5 +/- 3.5% (P < 0.01) and 95.3 +/- 4.3% (P < 0.01) in response to 5 x 10(-7) M, 10(-6) M, 5 x 10(-6) M and 10(-5) M propofol, respectively. CONCLUSION: Propofol dose-dependently inhibits PDBu-induced, PKC-mediated contraction of rat aortic smooth muscle.     

Inhibitory Effects of Propofol on Intracellular Signaling by Endothelin-1 in Aortic Smooth Muscle Cells

Background: Blood pressure decreases when propofol is administered. However, the exact mechanism underlying the vascular effects of propofol has not yet been elucidated. Endothelin produced by vascular endothelial cells is a potent vasoactive peptide that elicits prolonged contraction of vascular smooth muscle cells. The effects of propofol on endothelin-1-induced intracellular signaling in an aortic smooth muscle cell line, A10 cells, were examined.

Methods: Cultured A10 cells were pretreated with propofol for 20 min and then stimulated with endothelin-1. The effect of propofol on the endothelin-1-induced Ca2+ influx into A10 cells was evaluated by measuring intracellular45 Ca2+. The effects of propofol on the endothelin-1-induced activation of phosphatidylinositol-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D were evaluated by measuring the formation of inositol phosphates and choline, respectively. The effect of propofol on endothelin-1 binding to its receptor was determined by an [sup 125 I] endothelin-1-binding assay.

Results: Propofol inhibited the the endothelin-1-induced Ca2+ influx, but this was significant only at supuraclinical concentrations. The endothelin-1-stimulated formation of inositol phosphates was significantly suppressed by propofol. However, propofol had no effect on the formation of inositol phosphates induced by NaF, an activator of heterotrimeric guanosine triphosphate (GTP)-binding proteins. Propofol inhibited the endothelin-1-induced formation of choline. Propofol had no effect on the binding of endothelin-1 to its receptor.     

The relaxant effect of propofol on guinea pig tracheal muscle is independent of airway epithelial function and beta-adrenoceptor activity.

Airway epithelium and vascular endothelium modulate the tension of the underlying smooth muscle by releasing relaxing factors such as prostanoids and nitric oxide (NO). We investigated whether the relaxant effect of propofol on airway smooth muscle is dependent on airway epithelial function. Tracheal spirals of female guinea pigs were mounted in water-jacketed organ baths filled with Krebs-bicarbonate buffer aerated with 95% O2 and 5% CO2 at 37 degrees C. Changes in isometric tension of the specimens were measured with a force-displacement transducer and recorded with a polygraph. Propofol (10(-4) to 10(-3) M) inhibited carbachol (CCh)-, histamine (HA)-, or endothelin-1-induced contractions of the muscles in a dose-dependent manner. Neither mechanical removal of the epithelial layer, chemical inhibition of epithelial synthesis of prostanoids, nor NO affected the relaxant effect of propofol on CCh- or HA-induced tracheal contraction. Furthermore, the blockade of beta-adrenoceptors did not change the relaxant effect of propofol. These results indicate that the relaxant effect of propofol on the airway smooth muscle is independent of the epithelial function or beta-adrenoceptor activity. Propofol is an excellent anesthetic for patients with hyperreactive airways in which the epithelial layer is damaged. IMPLICATIONS: Airway epithelium, as well as vascular endothelium, plays an important role in modulating the baseline tone and reactivity of underlying smooth muscle. We investigated, in vitro, whether the relaxant effect of propofol on airway smooth muscle is dependent on airway epithelial function. We suggest that propofol relaxes airway smooth muscle independently of the epithelial function.     

Propofol attenuates angiotensin II-induced vasoconstriction by inhibiting Ca2+-dependent and PKC-mediated Ca2+ sensitization mechanisms

Purpose

Angiotensin II (Ang II)-induced vascular contraction is mediated by Ca²⁺-dependent mechanisms and Ca²⁺ sensitization mechanisms. The phosphorylation of protein kinase C (PKC) regulates myofilament Ca²⁺ sensitivity. We have previously demonstrated that sevoflurane inhibits Ang II-induced vasoconstriction by inhibiting PKC phosphorylation, whereas isoflurane inhibits Ang II-induced vasoconstriction by decreasing intracellular Ca²⁺ concentration ([Ca²⁺]_i) in vascular smooth muscle. Propofol also induces vasodilation; however, the effect of propofol on PKC-mediated myofilament Ca²⁺ sensitivity is poorly understood. The aim of this study is to determine the mechanisms by which propofol inhibits Ang II-induced vascular contraction in rat aortic smooth muscle.

Methods

An isometric force transducer was used to investigate the effect of propofol on vasoconstriction, a fluorometer was used to investigate the change in [Ca²⁺]_i, and Western blot testing was used to analyze Ang II-induced PKC phosphorylation.

Results

Ang II (10^?7?M) elicited a transient contraction of rat aortic smooth muscle, which was associated with an elevation of [Ca²⁺]_i. Propofol (10^?6?M) inhibited Ang II-induced vascular contraction (P?<?0.01) and increase in [Ca²⁺]_i (P?<?0.05) in rat aortic smooth muscle. Ang II also induced a rapid increase in [Ca²⁺]_i in cultured vascular smooth muscle cells, which was suppressed by propofol (P?<?0.05). Propofol (10^?6?M) attenuated Ang II-stimulated PKC phosphorylation (P?<?0.05).

Conclusion

These results suggest that the inhibitory effect of propofol on Ang II-induced vascular contraction is mediated by the attenuation of a Ca²⁺-dependent pathway and Ca²⁺ sensitivity through the PKC signaling pathway.