INTERACTIONS BETWEEN THE CIRCULATORY EFFECTS OF CENTRAL HYPOVOLAEMIA AND ARTERIAL HYPOXIA IN CONSCIOUS RABBITS

1. Eight conscious rabbits were repeatedly subjected to progressive reduction in central blood volume by gradually inflating a thoracic inferior vena caval-cuff so cardiac index (CI) fell at a constant 8.5% of baseline/min. 2. Caval-cuff inflations were performed after 10 min exposure to 100, 21, 12–14 and 8–10% O₂, with and without the addition of 3–4% CO₂, in randomized order. 3. The haemodynamic response to progressive reduction in central blood volume was biphasic. In Phase I, systemic vascular conductance index (SVCI) fell linearly, supporting mean arterial pressure (MAP). When CI had fallen to a critical level, Phase II occurred in which SVCI rose abruptly, MAP plummeted and respiratory drive progressively increased. 4. During Phase I, there were independent linear relationships between Pao₂ (but not Pao₂) and the rates at which SVCI and MAP changed during the progressive fall of CI. The higher the level of Pao₂, the greater was the rate of fall of SVCI and the less the rate of fall of MAP. 5. There was an inverted U-shaped effect of Pao₂, on the level of CI at which Phase II occurred: (a) during hyperoxia (100% O₂), Phase II occurred later than during normoxia (21% O₂); and (b) across the normoxic and hypoxic gas mixtures (21–8% O₂, with and without added CO₂), there was an independent linear relationship between Pao₂ (but not Pao₂ or Pao₂×Pao₂) and the level of CI at which Phase II occurred. That is, the lower the level of Pao₂, the later was the onset of Phase II. This interaction is best explained by an increased level of central sympathetic vasoconstrictor drive during hypoxia.     

格隆溴铵对高氧诱导幼鼠急性肺损伤的影响及其机制研究

目的 探究格隆溴铵对高氧诱导幼鼠急性肺损伤（ALI）的影响及作用机制。方法 从30只SD幼鼠中随机选取10只为对照组,其余幼鼠成功复制高氧诱导的ALI模型,随机分为ALI组、格隆溴铵组,每组10只。格隆溴铵组雾化吸入0.8 mg/（kg·d）格隆溴铵,ALI组、对照组吸入等体积生理盐水,连续给药7 d后,测量幼鼠肺组织湿/干重比值（W/D）、肺指数,检测白细胞介素-1β（IL-1β）、白细胞介素-6（IL-6）及肿瘤坏死因子-α（TNF-α）水平及血清活性氧基团（ROS）、超氧化物歧化酶（SOD）水平,比较肺组织病理学变化及Toll样受体4/髓分化因子88（TLR4/MyD88）通路蛋白的表达。结果 与对照组比较,ALI组W/D及肺指数升高（P <0.05）,血清IL-1β、IL-6、TNF-α、SOD水平升高（P <0.05）,ROS水平降低（P <0.05）,TLR4、MyD88蛋白相对表达量上调（P <0.05）;与ALI组比较,格隆溴铵组W/D及肺指数降低（P <0.05）,血清IL-1β、IL-6、TNF-α、SOD水平降低（P <0.05）,ROS水平升高（P <0.05）,TLR4、MyD88蛋白相对表达量下调（P <0.05）。结论 格隆溴铵能改善血清炎症指标及氧化应激指标,降低高氧诱导的ALI,其作用机制可能与TLR4/MyD88通路有关。     

In vivo and in vitro models demonstrate a role for caveolin-1 in the pathogenesis of ischaemic acute renal failure

Caveolae and their proteins, the caveolins, transport macromolecules; compartmentalize signalling molecules; and are involved in various repair processes. There is little information regarding their role in the pathogenesis of significant renal syndromes such as acute renal failure (ARF). In this study, an in vivo rat model of 30 min bilateral renal ischaemia followed by reperfusion times from 4 h to 1 week was used to map the temporal and spatial association between caveolin-1 and tubular epithelial damage (desquamation, apoptosis, necrosis). An in vitro model of ischaemic ARF was also studied, where cultured renal tubular epithelial cells or arterial endothelial cells were subjected to injury initiators modelled on ischaemia-reperfusion (hypoxia, serum deprivation, free radical damage or hypoxia-hyperoxia). Expression of caveolin proteins was investigated using immunohistochemistry, immunoelectron microscopy, and immunoblots of whole cell, membrane or cytosol protein extracts. In vivo, healthy kidney had abundant caveolin-1 in vascular endothelial cells and also some expression in membrane surfaces of distal tubular epithelium. In the kidneys of ARF animals, punctate cytoplasmic localization of caveolin-1 was identified, with high intensity expression in injured proximal tubules that were losing basement membrane adhesion or were apoptotic, 24 h to 4 days after ischaemia-reperfusion. Western immunoblots indicated a marked increase in caveolin-1 expression in the cortex where some proximal tubular injury was located. In vitro, the main treatment-induced change in both cell types was translocation of caveolin-1 from the original plasma membrane site into membrane-associated sites in the cytoplasm. Overall, expression levels did not alter for whole cell extracts and the protein remained membrane-bound, as indicated by cell fractionation analyses. Caveolin-1 was also found to localize intensely within apoptotic cells. The results are indicative of a role for caveolin-1 in ARF-induced renal injury. Whether it functions for cell repair or death remains to be elucidated.     

γ干扰素和转化生长因子β1在高氧肺损伤中的表达及其意义

目的动态观测高氧肺损伤动物模型中（IFN-γ）和转化生长因子β1（TGF—β1）的变化规律，探讨高氧肺损伤纤维化的发病机制。方法取2周左右的Wistar大鼠32只，随机分为空气组和高氧暴露3、7、14d组，采用逆转录聚合酶链反应（RT-PCR）和免疫组织化学染色观察IFN-γ和TGF-β1在空气和高氧暴露3、7、14d组肺组织中的分布和表达。结果IFN-γ mRNA在高氧3d达高峰水平，高氧7d后开始下降，高氧14d下降更为明显，与空气组比较P分别〈0．05，〉0．05，〉0．05；TGF-β1 mRNA的表达在高氧3、7、14d均明显高于空气组（P均〈0．05）；高氧3d IFN-γ／TGF-β1比值显著增高（P〈0.05），高氧7d开始下降（P〉0．05），高氧14d明显下降（P〈0．05）。免疫组织化学染色也显示了基本一致的动态变化趋势。结论高氧肺损伤早期，IFN-γ的升高促进了高氧肺损伤炎症的发展；高氧肺损伤中晚期IFN-γ和TGF-β1的失衡可能是促进高氧肺损伤纤维化发展的原因。     

细胞色素b在早产新生大鼠高氧肺损伤肺组织中的表达和意义

目的探讨细胞色素b（cytochrome b，Cytb）与高氧肺损伤发生、发展的关系。方法早产新生SD（Sprague-Dawley）大鼠生后1d随机分为空气组、高氧组，高氧组持续暴露于常压氧舱中，氧浓度〉85％；空气组置于同一室常压空气中。两组分别于高氧或空气暴露后1、4、7、10和14d时提取肺组织RNA，采用半定量逆转录聚合酶链反应（RT-PCR）测定CytbmRNA表达；同时应用免疫组化方法检测肺组织切片中Cytb蛋白表达；应用Western-blot检测高氧肺损伤肺组织中Cytb蛋白水平的表达变化。结果与空气组相比，高氧暴露1d、4d CytbmRNA含量及其表达显著增强（P〈0．05）；7d后Cytb呈下降趋势，其表达较空气组减弱，但两者相比差异无统计学意义（P〉0．05）。高氧暴露后，随日龄变化肺组织Cytb免化结果与CytbmRNA表达相似；与空气组相比，高氧暴露1d、4d肺组织Cytb表达显著增强（P〈0．05）；7d后Cytb呈逐渐下降趋势，其表达较空气组减弱，但7、10d两组相比差异无统计学意义，14d极显著减弱（P〈0．01）。Western-blot实验结果：与空气组相比，高氧暴露1d、4dCytb蛋白水平表达增强但两组相比差异无统计学意义（P〉0．05）；7d后Cytb呈下降趋势，其表达较空气组减弱，但7、10d两组相比差异无统计学意义（P〉0．05），而14d显著减弱（P〈0．05）。结论85％高浓度氧暴露诱导早产新生大鼠线粒体编码的Cytb异常表达，这种变化可能参与高氧肺损伤的发生。     

维甲酸对新生大鼠高氧肺损伤的干预作用

目的探讨高氧暴露新生大鼠肺组织结构的变化和连接蛋白Connexin26(Cx26)的表达情况及维甲酸对其影响。方法24只3日龄SD大鼠随机分为3组:高氧暴露维甲酸组(维甲酸组)、高氧暴露安慰组(高氧组)、空气暴露对照组(对照组);采用950mL/L氧体积分数条件下制作新生大鼠高氧肺损伤模型;观察大鼠一般情况,用HE染色法观察肺组织结构变化及辐射状肺泡计数(RAC),免疫组织化学检测Cx26的表达。结果体质量、RAC等方面与空气组相比,高氧组、维甲酸组均有显著差异[(13.53±1.27)、(13.38±1.29)、(17.37±0.89)g,F=30.19P=0;(11.15±1.33)、(12.49±1.47)、(13.94±0.98),F=9.59P=0];Cx26蛋白在空气组表达比较局限,高氧组弥散表达,而维甲酸组更多表达;阳性细胞分别为(13.68±1.28)%、(17.82±1.72)%、(19.69±1.77)%,F=29.36P=0。结论维甲酸对新生大鼠高氧肺损伤具有保护作用,可能与间隙连接蛋白Cx26表达的改变有密切的关系。     

降钙素基因相关肽对高氧暴露胎鼠原代肺泡Ⅱ型细胞的保护作用及其Wnt信号机制

目的探讨降钙素基因相关肽(calcitonin generelated peptide,CGRP)是否可促进高氧损伤肺泡Ⅱ型上皮细胞(typeⅡalveolar epithelial cells,AECⅡ)的存活及其可能涉及的Wnt信号机制。方法 SD胎鼠原代AECⅡ分为空气组、高氧组、高氧+CGRP组、高氧+CGRP+hCGRP8-37组,采用MTT测定各组细胞增殖,流式细胞仪检测细胞死亡,Western blot检测Wnt7b、β-catenin及p-β-catenin表达。结果与空气组对照比较,高氧暴露24 h后死亡细胞数显著升高(P<0.01),细胞增殖活性明显受到抑制(P<0.01),CGRP干预可明显下调高氧暴露后死亡细胞数(P<0.01),减弱高氧对细胞增殖的抑制作用(P<0.01)。高氧暴露后Wnt7b及β-catenin蛋白表达水平明显降低(P<0.01),p-β-catenin表达水平显著增加(P<0.01),CGRP干预后,与单纯高氧暴露组相比Wnt7b、β-catenin蛋白表达水平增加,而p-β-catenin表达水平降低,具统计学差异(P<0.01)。结论 CGRP可减少高氧诱导的细胞死亡、减弱高氧对细胞增殖的抑制效应,改善AECⅡ存活,Wnt7b/β-catenin通路可能参与了CGRP这一调控过程。