平滑肌非钙依赖性收缩的生化机理

平滑肌收缩的原发信号一般来自肌浆中游离Ｃａ２＋浓度的增高．在调钙蛋白（Ｃａｌｍｏｄｕｌｉｎ,ＣａＭ）参与下,肌球蛋白轻链激酶（ＭＬＣＫ）被激活,从而催化肌球蛋白的磷酸化,启动平滑肌的横桥循环（ｃｒｏｓｓｂｒｉｄｇｅｃｙｃｌｉｎｇ）．除平滑肌收缩的钙依赖性调控外,也存在非钙依赖性调控的生化机理．这一条信号转导途径,可经由Ｇ蛋白以激活非钙依赖性蛋白激酶Ｃ的同工酶ＰＫＣ－ε,其下游步骤有两种钙结合蛋白（ｃａｌｐｏｎｉｎＣａＰ与Ｃａｌｄｅｓｍｏｎ,ＣａＤ）发挥了直接或间接靶蛋白的重要作用．     

神经节苷脂（Gangliosides）对人红细胞膜Ca~（2＋）－Mg~（2＋）ATPase的影响

神经节苷脂（Ｇａｎｇｌｉｏｓｉｄｅｓ）是红细胞膜Ｃａ~（２＋）－Ｍｇ~（２＋）ＡＴＰａｓｅ的一种激活剂,这种激活作用也是依赖于Ｃａ~（２＋）存在。在２００μｍｏｌ／ＬＣａ~（２＋）存在的反应体系中,１００μｇ／ｍＬＧａｎｇｌｉｏｓｉｄｅｓ对Ｃａ~（２＋）－Ｍｇ~（２＋）ＡＴＰａｓｅ的激活作用最大,为基本酶活性的１５０％以上。实验还发现ＣａＭ拮抗剂三氟拉嗪（ＴＦＰ）、粉防已碱（Ｔｅｔ）等也同样抑制Ｇａｎｇｌｉｏｓｉｄｅｓ的这种激活作用。其抑制的ＩＣ_（５０）值为２５μｍｏｌ／Ｌ和３０μｍｏ１／Ｌ;而此浓度下抑制剂存在的反应体系中,对Ｃａ~（２＋）－Ｍｇ~（２＋）ＡＴＰａｓｅ的基本活性影响不大。     

缺氧心肌收缩蛋白Ca~（2＋），Mg~（2＋）－ATP酶活性研究

将大鼠置于模拟海拔８ｋｍ高度的低压舱内缺氧１周及缺氧后空气中常氧恢复１周和２周,观察了左右心室功能、心肌肥厚、心肌收缩蛋白含量及其Ｃａ￣（２＋）,Ｍｇ￣（２＋）－ＡＴＰ酶活性的动态变化。结果表明,８ｋｍ缺氧１周后肺动脉压及右心室收缩压明显升高,左右心室±ｄｐ／ｄｔｍａｘ及收缩指数明显降低。左右心室肌明显肥厚,心肌收缩蛋白Ｃａ￣（２＋）,Ｍｇ￣（２＋）－ＡＴＰ酶活性明显减低。缺氧后常氧恢复１和２周后,左右心室功能逐渐恢复达到或接近正常水平,心肌肥厚逐渐减轻或恢复正常,心肌收缩蛋白Ｃａ￣（２＋）,Ｍｇ￣（２＋）－ＡＴＰ酶活性也逐渐升高。因此说明：心肌收缩蛋白Ｃａ￣（２＋）,Ｍｇ￣（２＋）－ＡＴＰ酶活性的改变是心功能变化的重要生化基础之一,它的减低是缺氧心肌对环境的代偿适应。     

经G—蛋白敏感的跨膜信号通路调控心血管肌源性张力

本研究探讨低氧和ＡｌＦ－４等药物经Ｇ－蛋白敏感的跨膜信号通路对心血管肌源性张力的调控作用。在含有稳定表达Ｎａ＋－Ｃａ２＋交换蛋白的ＣＫ１．４细胞中,用ｆｕｒａ－２荧光影像确定细胞低氧对胞浆游离Ｃａ２＋［Ｃａ２＋］ｉ的影响。在离体犬心乳头肌、颈动脉、主动脉及肺动脉恒温灌流样本中,用张力－电换能器测量低氧灌流和ＡｌＦ－４等药物对心血管肌源性张力的影响。在整体犬体内,按拉丁方设计,用１２５Ｉｓｏｄ－１获得不同剂量ＶＩＳＡ高效剂细胞内分布等药代动力学参数。结果表明：①在ＣＫ１．４细胞中,低氧抑制Ｎａ＋－Ｃａ２＋交换蛋白,产生Ｃａ２＋内流,升高［Ｃａ２＋］ｉ;②低氧灌流削弱ＡｌＦ－４所致的血管收缩而明显易化Ｃａ２＋内流所致的心乳头肌收缩,与结果１）吻合;③ＶＩＳＡ高效剂分布至细胞内,协同ＡｌＦ－４,模拟并激活Ｇ－蛋白敏感的跨膜信号通路,显著改善低氧所致的Ｎａ＋－Ｃａ２＋交换蛋白等跨膜大分子和心血管收缩蛋白氧化损害。     

慢性低氧性肺动脉高压鼠原代培养肺动脉平滑肌细胞内钙的检定

用共聚焦激光扫描显微镜观察经Ｆｌｕｏ－３／ＡＭ负荷的慢性低氧性肺动脉高压（ＨＰＨ）大鼠原代培养的肺动脉平滑肌细胞（ＰＡＳＭＣ）的形态与内游离Ｃａ２＋浓度的动态变化。结果表明：原代培养的（ＨＰＨ）大鼠的ＰＡＳＭＣ与正常大鼠相比,①细胞内游离Ｃａ２＋浓度增加,但其收缩性减弱;②随培养日数增加,咖啡因（Ｃａｆｅｉｎ）所致的细胞内储钙池－肌浆网的Ｃａ２＋释放作用逐渐减弱,直至消失;③血管紧张素Ⅱ（ＡＴ－Ⅱ）升高细胞内钙作用明显增强;④部分呈大红色细胞对多种缩血管物质敏感性增强。结果提示,ＨＰＨ大鼠的ＰＡＳＭＣ的内钙明显增加,其调节机制处于紊乱状态。     

高血压大鼠红细胞膜Ca~（2＋），Mg~（2＋）─ATP酶对Ca~（2＋）反应的变化及Mg~（2＋）的作用

本实验观察了正常及高血压大鼠红细胞膜Ｃａ２＋,Ｍｇ２＋－ＡＴＰ酶对不同浓度Ｃａ２＋及Ｍｇ２＋的反应。结果表明：（１）在自发性高血压大鼠（ＳＨＲ）,此酶最适反应的Ｃａ２＋浓度为１０－６ｍｏｌ／Ｌ;ＷＫＹ大鼠为１０－４ｍｏｌ／Ｌ;两肾一环型肾性高血压大鼠（ＲＨＲ）为１０－７ｍｏｌ／Ｌ,Ｗｉｓｔａｒ大鼠为１０－４ｍｏｌ／Ｌ,Ｃａ２＋高于以上各相应浓度时该酶活性受到抑制;（２）作为该酶激动剂的Ｍｇ２＋有其最适激活浓度,在ＷＫＹ大鼠、ＲＨＲ及Ｗｉｓｔａｒ大鼠均为４．５ｍｏｌ／Ｌ;（３）高浓度Ｍｇ２＋（３６．０ｍｏｌ／Ｌ）可以逆转高浓度Ｃａ２＋对该酶的抑制作用。以上结果表明,底物Ｃａ２＋浓度的变化对Ｃａ２＋,Ｍｇ２＋－ＡＴＰ酶的催化活性影响极大,该酶活性的促发及维持必须有适宜浓度的Ｍｇ２＋。高血压时此酶对Ｃａ２＋的敏感性增高,且Ｍｇ２＋对酶保护作用更为明显。本结果提示,胞内高浓度Ｃａ２＋不仅是高血压发生的原因之一,并可能与其发展及恶化有关。     

低氧、血管紧张素Ⅱ对肺内小动脉平滑肌细胞膜Ca2 ┐ATPase活力的影响

本课题观察了低氧及血管紧张素Ⅱ（ａｎｇｉｏｔｅｎｓｉｎⅡ,ＡｎｇⅡ）对分离培养家兔肺内小动脉平滑肌细胞（ＰＡＳＭ－Ｃｓ）膜Ｃａ２＋－ＡＴＰａｓｅ活力的影响,同时用钙通道阻断剂维拉帕米（ｖｅｒａｐａｍｉｌ,ＶＰ）进行干预,进一步了解细胞内钙与Ｃａ２＋－ＡＴＰａｓｅ活力的关系。结果表明：ＰＡＳＭＣｓ膜Ｃａ２＋－ＡＴＰａｓｅ活力对低氧具有短暂的耐受性,随低氧时间延长,Ｃａ２＋－ＡＴＰａｓｅ活力呈时间依赖性抑制;低氧、ＡＮＧⅡ均能抑制Ｃａ２＋－ＡＴＰａｓｅ活力（Ｐ＜０．０１）低氧＋ＡⅡ对Ｃａ２＋－ＡＴＰａｓｅ活力的抑制具叠加效应（Ｐ＜０．０５）;ＶＰ可逆转低氧、ＡｎｇⅡ、低氧＋ＡｎｇⅡ对Ｃａ２＋－ＡＴＰａｓｅ活力的抑制（Ｐ＜０．０１）。结果提示：低氧,ＡＮＧⅡ可通过抑制肺血管平滑肌细胞膜Ｃａ２＋－ＡＴＰａｓｅ活力而可能削弱肺血管平滑肌舒张功能也可能是低氧性肺动脉高压（ＨＰＨ）形成的原因之一。     

PAF对肺内小动脉平滑肌细胞TXA_2，PGI_2乃Ca~（2＋）－ATPase的影响

本工作采用分离培养家兔肺内小动脉平滑肌细胞（ＰＡＳＭＣｓ），观察了外源性血小板活化因子（ｐｌａｔｅｌｅｔａｃｔｉｖａｔｉｎｇｆａｃｔｏｒ，ＰＡＦ）、ＢＮ５２０２１（ＰＡＦ受体拮抗剂）、吲哚美辛、维拉帕米对ＰＡＳＭＣｓ产生血栓素Ａ_２（ＴｘＡ_２）、前列环素（ＰＧＩ_２）及对细胞膜Ｃａ~（２＋）－ＡＴＰａｓｅ活力的影响。结果表明：（１）基础状态下ＰＡＳＭＣｓ存在花生四烯酸（ＡＡ）代谢。（２）外源性ＰＡＦ通过受体后途径激活环加氧酶促进ＡＡ代谢致ＴＸＡ_２及ＰＧＩ－２增加，ＴＸＡ_２／ＰＧＩ_２比值无明显变化。（３）外源性ＰＡＦ能直接抑制Ｃａ~（２＋）－ＡＴＰａｓｅ活力。（４）维拉帕米可逆转ＰＡＦ抑制ＰＡＳＭＣｓ膜Ｃａ~（２＋）－ＡＴＰａｓｅ活力的效应。     

糖皮质激素对肝细胞内游离钙的作用

应用钙离子荧光指示剂ｆｕｒａ－２,对糖皮质激素（Ｇｌｕｃｏｃｏｒｔｉｃｏｉｄ,ＧＣ）是否影响肝细胞内游离钙（Ｉｎｔｒａｃｅｌｌｕｌａｒ　ｆｒｅｅ　ｃａｌｃｉｕｍ,［Ｃａ２＋］ｉ作了初步探讨。结果发现,ＧＣ在短期内能升高肝细胞［Ｃａ２＋］ｉ,水平,并具有明显的量效关系。以１．０μｍｏｌ／Ｌ的Ｃｏｒｔｉｓｏｌ和１０．０μｍｏｌ／Ｌ的Ｄｅｘａｍｅｔｈａｓｏｎｅ效果最好。加入１．０μｍｏｌ／Ｌ的Ｃｏｒｔｉｓｏｌ０．２５ｍｉｎ即可引起肝细胞［Ｃａ２＋］ｉ的明显升高,到１０分钟时效应达高峰。此时与静息状态的肝细胞［Ｃａ２＋］ｉ水平相比,胞浆内游离钙升高了近３倍;与相应对照组比较,胞浆内游离钙升高具有明显的统计学意义,Ｐ＜０．０１。ＲＵ４８６为一种人工合成的糖皮质激素受体（Ｇｌｕｃｏｃｏｒｔｉｃｏｉｄ　ｒｅｃｅｐｔｏｒ,ＧＲ）的拮抗剂,它可以取消ＧＣ升高肝细胞［Ｃａ２＋］ｉ的效应,提示ＧＣ升高肝细胞内［Ｃａ２＋］ｉ可能与ＧＲ介导有一定关系。鉴于ＧＣ升高［Ｃａ２＋］ｉ时间较短,推测与肝细胞膜ＧＲ的非基因快速调节作用影响钙离子通道有关。     

药物诱导后的人大肠癌细胞的[Ca^2＋]i的变化

采用荧光分光光度计法检测维甲酸（ＲＡ）、１,２５（ＯＨ）２ＶＤ３及佛波酯（ＰＭＡ）诱导ＣＣＬ２２９细胞分化后［Ｃａ２＋］ｉ变化,并观察内质网（ＥＲ）特异的Ｃａ２＋－ＡＴＰａｓｅ抑制剂Ｔｈａｐｓｉｇａｒｇｉｎ（ＴＧ）、ＩＰ３受体抑制剂Ｈｅｐａｒｉｎ对ＲＡ诱导［Ｃａ２＋］ｉ变化的影响,从而探讨ＲＡ诱导［Ｃａ２＋］ｉ变化与ＥＲ的关系。结果显示：ＲＡ和１,２５（ＯＨ）２ＶＤ３在数秒内引起［Ｃａ２＋］ｉ显著升高。在ＥＧＴＡ和Ｖｅｒａｐａｍｉｌ预处理细胞条件下,ＴＧ不能抑制ＲＡ引起Ｃａ２＋从细胞内钙池中外流,ＲＡ作用后ＴＧ仍能升高［Ｃａ２＋］ｉ。另外,Ｈｅｐａｒｉｎ也不能完全抑制ＲＡ升高［Ｃａ２＋］ｉ。提示ＲＡ诱导大肠癌细胞升高［Ｃａ２＋］ｉ可能通过ＥＲ上ＩＰ３敏感性和非敏感性钙池,亦可能细胞内存在除ＥＲ外对ＲＡ敏感的钙池。     

RU486 antagonizes the inhibitory effect of peroxisome proliferator-activated receptor alpha on interleukin-6 production in vascular endothelial cells

Peroxisome proliferator-acitivated receptor alpha (PPARalpha) is a member of nuclear receptor superfamily. Recent studies have shown that the activators for PPARalpha inhibit the expression of some inflammatory molecules in vascular endothelial cells (ECs) and vascular smooth muscle cells, indicating the anti-inflammatory roles of PPARalpha on vascular walls. In this investigation, we showed that RU486, already proved to be an active anti-glucocorticoid and anti-progesterone agent, blocked the inhibition of tumor necrosis factor (TNF)-alpha-stimulated interleukin-6 (IL-6) production by the PPARalpha activator fenofibrate in human umbilical vein ECs. Transient transfection of bovine aortic ECs with an IL-6 promoter construct demonstrated that RU486 blocked the inhibitory effect of fenofibrate on TNF-alpha-induced IL-6 promoter activity. By fluorescence microscopy, RU486 was found to prevent fenofibrate-induced nuclear translocation of PPARalpha. Thus, RU486 has an antagonizing effect on PPARalpha-mediated down-regulation of IL-6 in vascular ECs. This effect may be exerted by its interference with the nuclear translocation of PPARalpha.     

Direct contractile effect of motilin on isolated smooth muscle cells of guinea pig small intestine.

We examined the direct effect of motilin on longitudinal and circular smooth muscle cells isolated from the guinea pig small intestine. In addition, the effects of 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxy-benzoate hydrochloride (TMB-8, an inhibitor of intracellular Ca(2+)-release), verapamil (a voltage-dependent Ca(2+)-channel blocker), and removal of extracellular Ca2+ were investigated to evaluate the role of intracellular Ca2+ stores and extracellular Ca2+ on the muscle contraction induced by motilin. The effects of atropine (a muscarinic receptor antagonist), spantide (a substance P receptor antagonist) and loxiglumide (a CCK-receptor antagonist) were also examined to determine whether the motilin-induced contraction was independent of those receptors. Motilin induced a contraction of the longitudinal and circular smooth muscle cells in a dose-dependent manner with the maximal effect attained after 30 seconds of incubation. The ED50 values were 0.3 nM and 0.05 nM, respectively. TMB-8 suppressed completely the motilin-induced contraction of both types of smooth muscle cells. Verapamil had only a slight suppressive effect. Removal of extracellular Ca2+ did not have any significant influence on motilin-induced contraction. The contractile response to motilin was not affected by atropine, spantide or loxiglumide. Our findings showed that:1) motilin has a direct contractile effect on both longitudinal and circular smooth muscle cells; 2) this contractile effect is not evoked via muscarinic, substance P or CCK receptors, and 3) the intracellular release of Ca2+ plays an important role in the contractile response to motilin on both types of smooth muscle cells.     

胃动素对大鼠胃平滑肌细胞收缩活动的作用

本研究用大鼠游离的胃平滑肌细胞,观察胃动素对胃平滑肌细胞的收缩作用。结果表明：（１）胃动素明显增强单个胃平滑肌细胞收缩活动,在生理剂量１０（－１１）─１０（－１０）ｍｏｌ范围内,呈剂量依赖性。（２）不同胃分区平滑肌细胞对冒动素兴奋反应不同,胃动素对胃窦平滑肌细胞收缩强度大于胃体和幽门。（３）给予抗胃动素血清可以完全取消胃动素对胃肌细胞的收缩反应,而阿托品、ＴＴＸ、甲氰米胍、ｌｏｘｉｇｌｕｍｉｄｅ均不影响胃动素的作用。（４）给予胞内钙释放阻断剂ＴＭＢ－８可抑制胃动素对目肌细胞的收缩作用。上述结果提示,胃动素对胃平滑肌细胞的直接作用是由胃动素受体所介导,且与胞内Ｃａ（２＋）释放起重要作用。     

Protein kinase C cross-talk with gonadotrope progesterone receptor is involved in GnRH-induced LH secretion

In the absence of progesterone (P), the anti-P at the receptor RU486 reduces basal and GnRH-stimulated LH secretion both in vivo and in vitro, demonstrating the existence of a ligand-independent activation of progesterone receptor (LIAPR). The aim of the present study was to determine which component of the intracellular LH secretory pathway activated by GnRH is responsible for LIAPR. To do this, anterior pituitary dispersed cells from female rats in proestrus, cultured in the presence of 17beta-estradiol, were incubated with activators or inhibitors of PKC, cAMP-PKA signalling pathways or intracellular calcium (Ca2+) traffic, in the presence or absence of RU486. Results showed that RU486 reduced both GnRH- and the PKC activator PMA-induced LH secretion. In GnRH-stimulated cells incubated with the PKC inhibitor BIS-I or treated with PMA "overnight", RU486 had no effect on reduced LH secretion, nor on stimulated LH secretion elicited by the Ca2+ ionophore ionomycin. Moreover, when GnRH- or PMA-treated cells were co-incubated with 1 microM of the L-type Ca2+ channel blocker nifedipine or the intracellular Ca2+ chelator BAPTA-AM, RU486 potentiated the expected inhibition of these drugs on LH secretion. Activation (forskolin, 8-Br-cAMP) or inhibition (MDL-12,330A) of the cAMP-PKA signalling cascade affected neither the GnRH- and PMA-induced increase of LH secretion nor the reduction of LH secretion due to RU486. Taken together, the data point to the existence of a Ca2+ -independent PKC-PR cross-talk mechanism as part of the intracellular signalling of GnRH-stimulated LH secretion.     

Evidence for separate binding sites for progesterone and RU486 in the chick oviduct

Binding characteristics of synthetic steroid, mifepristone (RU38486 - also referred to as RU486), were examined in cytosol prepared from the chick oviduct and the calf uterus, and were compared with those of progesterone and synthetic progestin R5020. Unlike [³H]progesterone binding, the [³H]RU486 binding in the oviduct cytosol did not saturate at 50 nM ligand concentration. The [³H]progesterone binding could not be eliminated in the presence of excess RU486, and [³H]RU486 binding was seen to be indisplaceable upon pretreatment of the chick oviduct cytosol with a 1000-fold excess progesterone. It is apparent that the chick oviduct cytosol is endowed with two separate sets of sites which interact with progesterone and RU486 independently. Furthermore, [³H]RU486 binding in the chick oviduct cytosol remained intact when incubated for 60 min at 37°C; it exhibited a single ionic form upon elution from DEAE-Sephacel and the [³H]RU486-associated radioactivity sedimented in the 4 S region both in salt-free and 0.3 M KCl-containing 5–20% sucrose gradients. In the calf uterus cytosol, both steroids exhibited comparable binding profiles. Our results provide evidence that chick oviduct possesses distinct binding sites that accept either progesterone or RU486, but not both, as is the case in the calf uterus.     

Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase

In Triton-skinned phasic ileal smooth muscle, constitutively active recombinant p21-activated kinase (PAK3) has been shown to induce Ca(2+)-independent contraction, which is accompanied by phosphorylation of caldesmon and desmin (Van Eyk JE, Arrell DK, Foster DB, Strauss JD, Heinonen TY, Furmaniak-Kazmierczak E, Cote GP, and Mak AS. J Biol Chem 273: 23433-23439, 1998). In the present study, we investigated whether PAK has a broad impact on smooth muscle in general by testing the hypothesis that PAK induces Ca(2+)-independent contractions and/or Ca(2+) sensitization in tonic airway smooth muscle and that the process is mediated via phosphorylation of caldesmon. In the absence of Ca(2+) (pCa > 9), constitutively active glutathione-S-transferase-murine PAK3 (GST-mPAK3) caused force generation of Triton-skinned canine tracheal smooth muscle (TSM) fibers to approximately 40% of the maximal force generated by Ca(2+) at pCa 4.4. In addition, GST-mPAK3 enhanced Ca(2+) sensitivity of contraction by increasing force generation by 80% at intermediate Ca(2+) concentrations (pCa 6.2), whereas it had no effect at pCa 4.4. Catalytically inactive GST-mPAK3(K297R) had no effect on force production. Using antibody against one of the PAK-phosphorylated sites (Ser(657)) on caldesmon, we showed that a basal level of phosphorylation of caldesmon occurs at this site in skinned TSM and that PAK-induced contraction was accompanied by a significant increase in the level of phosphorylation. Western blot analyses show that PAK1 is the predominant PAK isoform expressed in murine, rat, canine, and porcine TSM. We conclude that PAK causes Ca(2+)-independent contractions and produces Ca(2+) sensitization of skinned phasic and tonic smooth muscle, which involves an incremental increase in caldesmon phosphorylation.     

8-Bromo-cAMP decreases the Ca2+ sensitivity of airway smooth muscle contraction through a mechanism distinct from inhibition of Rho-kinase

To clarify whether cyclic AMP (cAMP)/cAMP-dependent protein kinase (PKA) activation and Rho-kinase inhibition share a common mechanism to decrease the Ca2+ sensitivity of airway smooth muscle contraction, we examined the effects of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP), a stable cAMP analog, and (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexane carboxamide dihydrochloride, monohydrate (Y-27632), a Rho-kinase inhibitor, on carbachol (CCh)-, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS)-, 4beta-phorbol 12,13-dibutyrate (PDBu)-, and leukotriene D4 (LTD4)-induced Ca2+ sensitization in alpha-toxin-permeabilized rabbit tracheal and human bronchial smooth muscle. In rabbit trachea, CCh-induced smooth muscle contraction was inhibited by 8-BrcAMP and Y-27632 to a similar extent. However, GTPgammaS-induced smooth muscle contraction was resistant to 8-BrcAMP. In the presence of a saturating concentration of Y-27632, PDBu-induced smooth muscle contraction was completely reversed by 8-BrcAMP. Conversely, PDBu-induced smooth muscle contraction was resistant to Y-27632. In the presence of a saturating concentration of 8-BrcAMP, GTPgammaS-induced Ca2+ sensitization was also reversed by Y-27632. The 8-BrcAMP had no effect on the ATP-triggered contraction of tracheal smooth muscle that had been treated with calyculin A in rigor solutions. The 8-BrcAMP and Y-27632 additively accelerated the relaxation rate of PDBu- and GTPgammaS-treated smooth muscle under myosin light chain kinase-inhibited conditions. In human bronchus, LTD4-induced smooth muscle contraction was inhibited by both 8-BrcAMP and Y-27632. We conclude that cAMP/PKA-induced Ca2+ desensitization contains at least two mechanisms: 1) inhibition of the muscarinic receptor signaling upstream from Rho activation and 2) cAMP/PKA's preferential reversal of PKC-mediated Ca2+ sensitization in airway smooth muscle.     

RU486对早孕猕猴海马GR的影响

目的探讨早孕猕猴给予大剂量RU486 3天后海马糖皮质激素受体(GR)的表达变化.方法 15只早孕猕猴随机分为空白对照组、赋形剂组和RU486组.空白对照组不予任何处理,赋形剂组和RU486组分别鼻饲赋形剂和RU486 3天.应用单克隆抗体链菌素亲生物蛋白过氧化酶(SP)免疫组织化学方法观察海马GR的表达情况,并用电子计算机图象分析技术进行处理.结果 RU486组猕猴妊娠终止,该组的海马GR表达显著下降,与对照组的差异有显著性.空白对照组和赋形剂组猕猴妊娠没有终止,其海马GR表达无差异.结论 RU486可使早孕猕猴海马的GR表达下降,推测这可能是该药终止妊娠的中枢作用机理之一.