硫化氢对乳鼠心肌细胞缺氧-复氧损伤的保护作用

目的:研究不同浓度的硫化氢(H_2S)对缺氧不同时间的乳鼠心肌细胞损伤的直接影响及其对复氧损伤的间接影响,分析其对乳鼠心肌细胞缺氧-复氧损伤的保护作用.方法:原代培养的乳鼠心肌细胞随机分为正常对照组、缺氧硫氢化钠(NaHS)0组、缺氧硫氢化钠 100 μmol/L组、缺氧硫氢化钠 200 μmol/L组、缺氧硫氢化钠400 μmol/L组以及缺氧-复氧硫氢化钠0组、缺氧-复氧硫氢化钠100 μmol/L组、缺氧-复氧硫氢化钠 200 μmol/L组、缺氧-复氧硫氢化钠 400 μmol/L组.在缺氧24 h、48 h、72 h后及复氧2 h后均检测细胞存活数量、培养液中乳酸脱氢酶(LDH)活性.结果:缺氧硫氢化钠100 μmol/L组、缺氧硫氢化钠200 μmol/L组和缺氧硫氢化钠 400 μmol/L组缺氧培养24 h、48 h和72 h后与各自时间点缺氧硫氢化钠0组比心肌细胞存活数量升高(P<0.01)、培养液中乳酸脱氢酶活性降低(P<0.01),差异均有统计学意义;缺氧硫氢化钠 200 μmol/L组和缺氧硫氢化钠 400 μmol/L组在缺氧培养24 h后较缺氧硫氢化钠100 μmol/L组心肌细胞存活数量升高(P<0.01)、培养液中乳酸脱氢酶活性降低(P<0.05～0.01),差异均有统计学意义.缺氧-复氧硫氢化钠100 μmol/L组、缺氧-复氧硫氢化钠200 μmol/L组和缺氧缺氧-复氧硫氢化钠400 μmol/L组缺氧培养24 h、48 h、72 h并复氧2 h后较各自时间点缺氧-复氧硫氢化钠0组比心肌细胞存活数量升高(P<0.01)、复氧后心肌细胞乳酸脱氢酶漏出量降低(P<0.01),差异均有统计学意义.结论:100~400 μmol/L 硫氢化钠对缺氧-复氧心肌细胞具有保护效果.200~400 μmol/L 硫氢化钠对缺氧24 h的心肌细胞保护作用较好.     

姜黄素对缺氧HepG2细胞中HIF-1α表达的影响及可能机制

目的:研究姜黄素对缺氧条件下人肝癌细胞HepG2中缺氧诱导因子-1α(HIF-1α)表达的影响,并探讨其可能机制.方法:0、1、2、5、10 μmol/L的姜黄素处理缺氧条件下的HepG2细胞6 h后,用Westernblot免疫印迹法和RT-PCR检测HIF-1α的蛋白及mRNA的表达:0 μmol/L,10 μmol/L姜黄素,10 μmol/L姜黄素 10 μmol/L MG-132处理缺氧条件下的HepG2细胞6 h后,用Western blot检测HIF-1α和VEGF的蛋白水平.结果:HepG2细胞经1、2、5、10 μmol/L的姜黄素处理后,HIF-1α蛋白水平与对照组(0μmol/L姜黄素处理)比较明显降低(F=79.81,P<0.01),且降低程度随着姜黄素处理浓度的增加而变大.但各剂量组HIF-1α的mRNA水平与对照组比较无显著性差异;蛋白酶体抑制剂MG-132可以逆转姜黄素所致的HepG2细胞HIF-1α和VEGF蛋白表达抑制(F=68.47,83.79,均P<0.01).结论:姜黄素通过蛋白酶体途径,在转录后水平抑制缺氧HepG2细胞HIF-1α表达.     

姜黄素对缺氧条件下HepG2细胞VEGF表达的影响

目的:研究姜黄素对缺氧条件下人肝癌细胞HepG2中血管内皮生长因子(VEGF)表达的影响.方法:姜黄素(0、1、2、5、10.mol/L)处理缺氧条件下的HepG2细胞6 h后,采用四唑盐(MTT)法观察HepG2细胞活性的变化,Western blot观察VEGF的蛋白水平变化,RT-PCR检测VEGF mRNA表达水平变化.结果:HqaG2细胞经1、2、5、10 μmol/L的姜黄素处理后,VEGF蛋白和mRNA水平与对照组(0μmol/L姜黄素处理)比较明显降低(蛋白:2.12±0.23,1.59±0.13,0.82±0.11,0.33±0.05 vs 2.85±0.37,P<0.05或P<0.01:mRNA:0.60±0.05,0.54±0.04,0.16±0.02,0.06±0.01 vs 0.81±0.07,均P<0.01),且降低程度随着姜黄素处理浓度的增加而变大.结论:姜黄素可抑制HepG2细胞中VEGF的基因表达.     

羟基红花黄色素A对缺氧心肌细胞的保护作用

目的观察羟基红花黄色素A(HSYA)对缺氧心肌细胞的保护作用。方法体外培养大鼠乳鼠心肌细胞,随机分为正常对照、缺氧损伤、HSYA1×10-6mol/L～1×10-10mol/L组、地尔硫艹卓组,同时设1×10-6mol/LHSYA正常对照组。以高纯氮气封罐,无糖无血清培养液密闭培养制备心肌细胞缺氧模型,观察各组细胞形态学变化,计数细胞搏动频率,测定心肌细胞存活率、细胞培养液中乳酸脱氢酶(LDH)活性、细胞内的丙二醛(MDA)浓度及ATP酶活性。结果与缺氧损伤组比较,1×10-7mol/L和1×10-8mol/L浓度HSYA组心肌细胞仍存在规律性搏动,细胞存活率显著升高,细胞培养液中LDH活性、心肌细胞内MDA的含量明显低于缺氧损伤组(P<0.05,P<0.01),而细胞内ATP酶的活性较缺氧损伤组显著增高(P<0.01)。结论1×10-7、1×10-8mol/L浓度的HSYA可有效的保护心肌细胞免受缺氧损伤。     

CoCl2缺氧处理对脐带间充质干细胞促血管生长因子表达的影响

目的: 探讨氯化钴(CoCl2)模拟缺氧预处理对人脐带间充质干细胞(UC-MSCs)中碱性成纤维生长因子(bFGF)和血管内皮生长因子(VEGF)基因表达及蛋白分泌的影响。方法: 分离、培养UC-MSCs。取第3代的UC-MSCs,运用含150 μmol/L的CoCl2培养液培养细胞72 h,用流式细胞仪检测缺氧对UC-MSCs表面标志物(CD34、CD45、CD90、CD105、CD29及CD49)的影响。依据CoCl2的浓度(0、50、100 μmol/L及150 μmol/L)将UC-MSCs分为4个组,即对照组、低、中、高CoCl2组,每个组处理24 h、48 h和72 h。用SYBRGREN荧光定量RT-PCR检测bFGF、VEGF mRNA的表达,用ELISA法检测bFGF和VEGF蛋白的表达。结果: 经含150 μmol/L CoCl2的培养液缺氧处理,没有改变细胞的形态和表面标记物。在缺氧培养时间相同的情况下,bFGF、VEGF基因的表达均随着CoCl2浓度的增加而增加,CoCl2为150μmol/L时达到峰值（P<0.05）。当CoCl2浓度为150μmol/L培养不同时间(24h、48 h及72 h)时,随着缺氧预处理时间的延长,bFGF、VEGF基因的表达随之增加,于48 h时达到峰值（P<0.05）,bFGF、VEGF基因的表达分别为8.15±0.10和16.67±0.17,延长缺氧培养的时间基因的表达减小（P<0.05）;蛋白与基因表达的变化基本一致。在含150 μmol/L CoCl2的培养液培养48 h,bFGF和VEGF的表达达到顶峰（P<0.05）,分别为(69.63±7.90) ng/L和(89.55±5.45) ng/L。结论: 适当浓度的CoCl2(<150 μmol/L)对UC-MSCs的生物学功能影响轻微。CoCl2可用于细胞的模拟缺氧,缺氧对UC-MSCs bFGF、VEGF的分泌具有时间和剂量依赖性,以含150 μmol/L CoCl2的培养液培养48 h,为促进bFGF、VEGF基因和其蛋白表达的最适条件。     

莱菔硫烷对H9C2心肌细胞缺氧/复氧损伤的保护作用

目的:探讨莱菔硫烷(sulforaphane,SFN)对H9C2心肌细胞缺氧/复氧损伤的保护作用。方法:H9C2心肌细胞随机分为3组:正常对照组、缺氧/复氧组(H/R组)和SFN预处理组(10μmol/L SFN预处理细胞12 h后,进行缺氧/复氧处理)。采用倒置显微镜观察各组细胞形态及凋亡程度,CCK8法检测各组H9C2心肌细胞存活率,Western blot法检测血红素氧化酶1(HO-1)、醌氧化还原酶1(NQO1)、Bcl-2和Bax蛋白的表达水平。结果:与正常对照组相比,H/R组和SFN预处理组心肌细胞存活率均降低(P均0.01),HO-1、NQO1、Bcl-2和Bax蛋白表达水平及Bcl-2/Bax均升高(P均0.01)。与H/R组相比,SFN预处理组的细胞生长状态较好,细胞存活率明显提高[(76.00±0.52)%对(55.73±0.43)%,P0.01],HO-1(3.24±0.01对1.86±0.01,P0.01)、NQO1(1.67±0.01对0.95±0.01,P0.01)和Bcl-2(0.70±0.00对0.48±0.01,P0.01)蛋白表达水平及Bcl-2/Bax(1.22±0.01对0.56±0.00,P0.01)均明显升高,Bax蛋白表达水平明显降低(0.57±0.00对0.85±0.01,P0.01)。结论:SFN对H9C2心肌细胞缺氧/复氧损伤有保护作用,可能与促进HO-1、NQO1、Bcl-2蛋白表达,抑制Bax蛋白表达有关。     

大鼠甲状旁腺素对体外培养心室肌细胞的促肥大作用

目的 观察不同浓度大鼠甲状旁腺素1-34（rat parathyroid hormone 1-34,rPTH1-34）对体外培养心室肌细胞的致肥大作用,观察细胞外信号调节激酶1/2（extracellular signal regulated kinases 1/2,ERK1/2）的变化。方法 体外培养新生大鼠心室肌细胞,以1×10-8～1×10-6 mol/L rPTH1-34分别孵育24 h,测定细胞直径、3H-亮氨酸(3H-Leu)掺入率、心房钠尿肽（atrial natriuretic peptide,ANP）mRNA、ERK1/2、磷酸化ERK1/2(p-ERK1/2)蛋白的表达。结果 与正常组相比,1×10-8 mol/L rPTH 1-34可使体外培养的心肌细胞直径、细胞蛋白合成速率轻度增加,ANP mRNA表达轻度升高,但无统计学意义;1×10-7,1×10-6 mol/L rPTH1-34 均可显著增加心肌细胞直径（P<0.01）,细胞蛋白合成速率（P<0.01）和ANP mRNA表达（P<0.01）。与正常组比较,PTH呈浓度依赖性地增加了ERK1/2和p-ERK1/2的表达（P<0.01）。结论 1×10-7,1×10-6 mol/L rPTH1-34能在体外诱导新生大鼠心室肌细胞发生肥大反应,且呈一定的浓度依赖性;PTH能呈浓度依赖性地刺激心肌ERK1/2过度表达。     

14-3-3蛋白在心肌细胞缺氧预处理中的表达及意义

目的:研究14-3-3蛋白在心肌细胞缺氧预处理中的表达及意义。方法:实验用SD新生大鼠(1～3d龄),雌雄不拘,无菌取出乳鼠心脏,经分离附着组织,胰蛋白酶消化,纯化制成心肌细胞。在培养的第4天随机分为3组:正常对照组、缺氧/复氧(A/R)组、缺氧预处理(APC)组。各组分别进行以下指标观察:①心肌细胞搏动频率;②细胞存活率(MTT法);③培养液中乳酸脱氢酶(LDH)活性;④透射电镜观察细胞超微结构;⑤Western Blotting法检测14-3-3蛋白的表达变化。RT-PCR法检测14-3-3蛋白η、σmRNA的表达变化。结果:A/R组和APC组的14-3-3蛋白表达均上调,分别是正常对照组的(3.61±0.37)倍和(5.52±0.49)倍,A/R组和APC组与正常对照组比较、A/R组与APC组比较,均P<0.01。A/R组、APC组心肌细胞14-3-3η亚型mRNA分别为正常对照组的(1.82±0.30)倍、(2.93±0.52)倍,差异均有统计学意义(P<0.01);APC组与A/R组比较,差异亦有统计学意义(P<0.01)。A/R组、APC组心肌细胞14-3-3σ亚型mRNA表达量分别为正常对照组的...     

缺氧对大鼠心肌细胞系H9C2中HIF-1α、CT-1表达的影响

目的 观察缺氧对大鼠心肌细胞系H9C2细胞中HIF-1、CT-1的影响.方法 采用向培养液中加氯化钴( CoCl2)模拟缺氧.实验分为缺氧组(培养液中加入100 μmol/L的CoCl2)和对照组(培养液中无CoCl2).通过CCK-8试剂盒检测各组H9C2细胞的存活率.通过Real-time PCR检测HIF-1α和CT-1的mRNA水平,通过Western blot技术检测HIF-1 α和CT-1的蛋白质水平.结果 缺氧3d和4d后,缺氧组H9C2细胞的存活率较对照组下降(P＜0.05),缺氧后H9C2细胞中HIF-1α mRNA表达无明显改变(P＞0.05),而蛋白表达增加(P＜0.05).缺氧后H9C2细胞中CT-1 mRNA和蛋白水平均增加(P均＜0.05).结论 缺氧环境下大鼠心肌细胞系H9C2中HIF-1α和CT-1的表达增加.     

粒细胞集落刺激因子对乳鼠缺氧心肌细胞的保护作用及机制探讨

目的研究粒细胞集落刺激因子(G-CSF)对缺氧心肌细胞的影响,探讨G-CSF发挥心肌细胞保护作用的分子机制。方法将心肌细胞分为3组,对照组、缺氧组和G-CSF组。流式细胞仪检测各组心肌细胞的存活率、凋亡率和坏死率。Northern blot法检测3组心肌细胞中Bcl-2、Bax、caspase-3 mRNA的表达,western blot法检测3组心肌细胞中细胞色素C(Cyt C)、信号转导与转录激活因子3(STAT-3)、caspase-3蛋白的表达。结果 6μg/LG-CSF开始发挥对缺氧心肌细胞的保护作用,150 μg/L保护作用最强,30μg/L和750μg/L保护作用相似。对照组、缺氧组和G-CSF组心肌细胞的存活率、凋亡率和坏死率差异有统计学意义。与缺氧组比较,G-CSF组Bcl-2mRNA表达增加,Bax、caspase-3 mRNA、Cyt C和caspase-3蛋白表达减少(P<0.01)。结论缺氧心肌细胞中,G-CSF可能通过线粒体途径发挥抗凋亡的作用。     

Adenoviral gene transfer of activated phosphatidylinositol 3'-kinase and Akt inhibits apoptosis of hypoxic cardiomyocytes in vitro

BACKGROUND: The intracellular signaling pathways that control cardiomyocyte apoptosis have not been fully defined. Because insulin-like growth factor-1 (IGF-1) prevents cardiomyocyte apoptosis, we examined the role of its downstream signaling molecules in an in vitro model of hypoxia-induced cardiomyocyte apoptosis. METHODS AND RESULTS: Treatment of rat neonatal cardiomyocytes with IGF-1 increased activity of both phosphatidylinositol 3' (PI 3)-kinase and its downstream target, Akt (also known as protein kinase B or PKB). Cardiomyocytes were subjected to hypoxia for 24 hours, and apoptosis was assessed by DNA laddering, TUNEL staining, and ELISA for histone-associated DNA fragments. IGF-1 treatment (100 nmol/L) reduced cardiomyocyte apoptosis, and this effect was inhibited by simultaneous treatment with a PI 3-kinase inhibitor. Cardiomyocytes were infected with either a control adenovirus (Ad.EGFP) or adenoviruses carrying constitutively active forms of PI 3-kinase (Ad.BD110) or Akt (Ad. myr-Akt-HA). Ad.BD110 significantly inhibited apoptosis of hypoxic cardiomyocytes compared with Ad.EGFP (61.0+/-4.6% less DNA fragmentation than in Ad.EGFP-infected cells, P<0.0001). Ad. myr-Akt-HA even more dramatically inhibited apoptosis of hypoxic cardiomyocytes (90.9+/-1.4% less DNA fragmentation than in controls, P<0.0001). CONCLUSIONS: IGF-1 activates PI 3-kinase and Akt in cardiomyocytes. Activated PI 3-kinase and Akt are each sufficient to protect hypoxic cardiomyocytes against apoptosis in vitro. Adenoviral gene transfer provides a useful tool for investigating the role of these signaling pathways in cardiomyocyte apoptosis.     

肿瘤抑制因子PTEN与心肌肥大关系的研究

目的 观察肿瘤抑制因子PTEN在心肌肥厚大鼠心肌组织以及在血管紧张素Ⅱ诱导的肥大心肌细胞中的表达,探讨PTEN在心肌肥大发生发展中的作用以及相关机制。方法采用腹主动脉狭窄术制备压力超负荷心肌肥厚动物模型,及血管紧张素Ⅱ诱导新生大鼠心肌细胞肥大模型,应用逆转录-聚合酶链式反应(RT-PCR)方法、Western blot及免疫组化等方法,分别检测各组PTEN mRNA和蛋白表达的变化,以及PTEN蛋白在心肌细胞中的定位。结果(1)与对照组相比,心肌肥厚组大鼠左室肌PTEN mRNA和蛋白表达均明显减少;血管紧张素Ⅱ诱导心肌细胞肥大组PTEN蛋白表达明显减少。(2)与心肌肥厚组相比,卡托普利组大鼠左室心肌PTEN mRNA和蛋白表达增加,接近对照组。(3)免疫组化实验结果显示心肌细胞胞核内有阳性免疫产物生成,提示PTEN蛋白定位于心肌细胞核内。结论PTEN在心肌肥大发生发展中可能起负调控作用,该作用与肾素-血管紧张素系统密切相关。     

蛋白激酶C和Ca2+在心肌细胞预处理中的作用

目的：探讨心肌细胞缺氧预处理、蛋白激酶C（PKC）和细胞内钙离子在心肌细胞预处理中的作用。方法：在培养乳鼠心肌细胞缺氧预处理的模型上，观察缺氧预处理以及PKC抑制剂Chelerythrine和钙离子螯合剂BAPTA／AM对缺氧预处理的影响。结果：缺氧预处理可以减少缺氧／复氧对心肌细胞的损伤。PKC抑制剂Chelerythrine和钙离子螯合剂BAPTA／AM可以抑制缺氧预处理的心肌保护作用。结论：PKC和钙离子介导心肌细胞的缺氧预处理。     

Melatonin protects periventricular white matter from damage due to hypoxia

Abstract: This study investigated the potential of melatonin in ameliorating hypoxic damage to the periventricular white matter (PWM) in the neonatal brain. Vascular endothelial growth factor (VEGF), nitric oxide (NO), glutathione (GSH) and malondialdehyde (MDA) content in the PWM of 1‐day‐old rats subjected to hypoxia for a period of 2 hr was examined. Vascular endothelial growth factor, NO and MDA concentration was increased whereas that of GSH was reduced after the hypoxic exposure. Additionally, degenerating axons, apoptotic and necrotic cells and vacuolation of capillary endothelial cells were observed in the PWM. The neighboring ependymal and choroid plexus cells also appeared to undergo structural alterations. Increased vascular permeability in the PWM of hypoxic rats was evidenced by the leakage of rhodamine isothiocyanate (RhIC) which was taken up by the amoeboid microglial cells. In vitro experiments showed increased apoptosis in OLN‐93 cells, an oligodendrocytic cell line, following hypoxic exposure. Hypoxic rats treated with melatonin showed reduced VEGF, NO and MDA concentrations, increased GSH content and reduced RhIC leakage in the PWM. The ultrastructure of axons, endothelial, ependymal and choroid plexus epithelial cells appeared relatively normal in the hypoxic animals treated with melatonin. The incidence of apoptotic OLN‐93 cells was also reduced with melatonin treatment. We suggest that the protective effects of melatonin on various parameters in the PWM of hypoxic neonatal brains were due to its antioxidant properties.     

生长激素对阿霉素中毒大鼠心肌细胞的抗凋亡作用

目的 :观察不同剂量生长激素 (GH)对阿霉素中毒所致大鼠心肌细胞凋亡的影响。方法 :建立体外培养的大鼠心肌细胞阿霉素损伤模型 ,加入不同剂量的生长激素 ,采用流式细胞仪 (FCM)检测心肌细胞凋亡和坏死率。以 2 ,3 二苯基溴化四唑 (MTT)比色法绘制心肌细胞生长曲线。结果 :阿霉素可导致心肌细胞损伤 ,表现为心肌细胞细胞坏死和凋亡发生率增高 ;GH能促进心肌细胞增殖并降低其凋亡率 ,在 10 μg·ml- 1 至 5 0 0 μg·ml- 1 范围内 ,其抗凋亡和促增殖作用呈剂量依赖性增强。结论 :GH对阿霉素中毒所致的心肌细胞凋亡有直接的抑制作用     

N-acetylcysteine attenuates PKCbeta2 overexpression and myocardial hypertrophy in streptozotocin-induced diabetic rats

OBJECTIVE: Oxidative stress-mediated activation of protein kinase C (PKC) beta(2) in the myocardium has been implicated in the development of cardiomyopathy. Overexpression of PKCbeta(2) is associated with increased expression of connective tissue growth factor (CTGF) in myocardium, resulting in myocardial hypertrophy. We hypothesized that chronic treatment with the antioxidant N-acetylcysteine (NAC) would normalize oxidative stress-mediated overexpression of myocardial PKCbeta(2) and CTGF and attenuate the development of myocardial hypertrophy. METHODS: Control and streptozotocin-induced diabetic rats were treated with NAC in drinking water for 8 weeks. At termination rats were surgically prepared for hemodynamic measurement, subsequent to which their hearts were removed to evaluate cardiac performance and histological and biochemical changes. Further, the role of PKCbeta(2) in hyperglycemia-induced cardiomyocyte hypertrophy was tested in cultured neonatal cardiomyocytes. RESULTS: Myocardial hypertrophy, characterized by an increased ratio of ventricle weight to body weight and cardiomyocyte cross-sectional area was found to be higher in untreated diabetic rats. Further, in myocardium, increased levels of 15-F(2t)-isoprostane were accompanied by an increased expression of membrane-bound PKCbeta(2) and CTGF. N-acetylcysteine treatment not only attenuated these changes but also prevented hyperglycemia-induced hypertrophy in cultured neonatal rat cardiomyocytes. CONCLUSIONS: The results suggest that PKCbeta(2) overexpression represents a mechanism causing hyperglycemia-mediated myocardial hypertrophy, which can be prevented by the antioxidant N-acetylcysteine.     

Statins initiated after hypertrophy inhibit oxidative stress and prevent heart failure in rats with aortic stenosis

OBJECTIVE: Heart failure is a major and escalating public health problem. Recent studies have demonstrated that statins prevented chronic heart failure (CHF) in animal studies. However, it is unknown whether statins therapy initiated after left ventricular (LV) hypertrophy is evident can still effectively prevent CHF. This study tested the hypothesis that statins can prevent the transition of hypertrophy to heart failure. METHODS AND RESULTS: The rats were studied at 6, 12, and 20 weeks after aortic stenosis (AS) operation. Some rats were given simvastatin (2.0 mg kg(-1) per day) from 13 weeks after AS operation for 8 weeks. Coarctation of aorta in rats resulted in compensatory LV hypertrophy (LVH), concomitant with an increase of superoxide levels and cardiomyocyte apoptosis in LV tissues at 12 weeks after AS operation. This was followed by CHF with a progressive increase in superoxide levels and cardiomyocyte apoptosis in LV tissues at 20 weeks after AS operation. Simvastatin treatment initiated from 13 weeks after AS operation significantly improved LV function and reduced superoxide levels and cardiomyocyte apoptosis in LV tissues. Pretreatment of simvastatin suppressed the hydrogen peroxide-induced apoptosis of cultured cardiomyocytes from neonatal rats. CONCLUSIONS: These data indicate that long-term administration of simvastatin improved LV function and prevented the transition of hypertrophy to CHF. Inhibition of oxidative stress and cardiomyocyte apoptosis may contribute to the benefits of simvastatin treatment on heart of rats with AS.     

Effects of neonatal hypoxia in the rat on inotropic stimulation of the adult heart

OBJECTIVE: To determine whether transient hypoxia in neonatal rats has long-lasting effects on inotropic stimulation of the adult heart. METHODS: The hearts of adult male Sprague-Dawley rats (89+/-1 (S.E.M.) days, 432+/-5 g) were studied. Half the animals had been subjected to neonatal hypoxia (FiO(2)=0.12, days 1-10) while the others had not. The peak response of left ventricular pressure (LVP) and the maximum rate of pressure increase (+dP/dtmax) were measured in isolated and perfused hearts during application of dobutamine, isoproterenol, milrinone and betaxolol. Left ventricular myocyte membranes were analyzed for beta receptor density, adenylyl cyclase activity and content. RESULTS: LVP and +dP/dtmax responses to stimulation with dobutamine and isoproterenol were significantly impaired in adult hearts of neonatally hypoxic rats. The inotropic effect of dobutamine was abolished by blockade with the beta(1)-selective antagonist betaxolol. The inotropic effects of the phosphodiesterase inhibitor milrinone were also significantly decreased in neonatally hypoxic adult hearts. There was no difference in left ventricular myocyte membrane beta receptor density of adult hearts whether they were hypoxic neonatally or not. However, left ventricular adenylyl cyclase activity on isoproterenol or forskolin stimulation and adenylyl cyclase levels (type V/VI) were significantly reduced in neonatally hypoxic adult hearts. CONCLUSIONS: Neonatal hypoxia in the rat has long-lasting effects on the left ventricular response to inotropic stimulation at maturity likely at least in part due to diminished left ventricular adenylyl cyclase levels.     

Endocrine changes in a rat model of chronic hypoxia mimicking cyanotic heart disease

OBJECTIVE: The endocrine system plays an important role in the adaptation to hypoxia. The aim of this study is to assess the effect of chronic hypoxia on endocrine changes in a neonatal animal model mimicking cyanotic heart disease. METHODS: Sprague-Dawley rats were placed in a normobaric hypoxic environment at birth and oxygen levels were maintained at 10% in an airtight Plexiglas chamber. Controls remained in room air. Animals were sacrificed at 4 and 8 weeks of life. Hematocrit, Free T4 (FT4), Thyrotropin (TSH), corticosterone, and Growth hormone (GH) were measured. RESULTS: Significant polycythemia developed in the hypoxic rats. Free T4 levels were significantly lower in the hypoxic (H) group compared to the control (C) group at 4 and 8 weeks with FT4 of 2.44 +/- 1.11 ng/dL (H) and 4.35 +/- 1.62 (C) at 4 weeks with a p value < 0.005 and FT4 of 2.01 +/- 0.36 (H) and 3.25 +/- 0.54 (C) ng/dL at 8 weeks with p < 0.01. At 8 weeks TSH levels were significantly lower in the hypoxic group (1.84 +/- 0.9 ng/mL (H) vs. 3.11 +/- 1.1 (C)) with p < 0.05. Corticosterone levels were higher in the hypoxic group with values of 126 +/- 14.8 ng/mL (H) and 114.1 +/- 12.6 (H) at 4 and 8 weeks respectively, when compared to the control group with values of 82.9 +/- 18.1 (C) and 92.7 +/- 10.3 (C) and 4 and 8 weeks with p < 0.0005 and < 0.05 respectively. Growth hormone levels were lower in the hypoxic group at 4 and 8 weeks with p < 0.05 and p < 0.001, respectively. CONCLUSION: Chronic hypoxia in our neonatal rat model was associated with decrease in growth hormone levels and an increase in corticosterone levels. Furthermore, hypoxia resulted in thyroid hormone axis suppression. This effect seems to centrally mediated.     

Immunoreactive erythropoietin concentrations in fetal and neonatal rats and the effects of hypoxia

Immunoreactive erythropoietin (Ep) was measured in normoxic and hypoxic (0.5 atm; 18 hours) fetal rats from day 14 to day 21 of gestation and in neonatal rats from birth to weaning, and was compared to the adult rat. Amniotic fluid (AF) Ep was approximately 100 mU/mL on day 14 and 15, and decreased to 20 mU/mL on day 20, with no difference between the hypoxic and normoxic mothers. Only on day 21 did the Ep in the AF increase slightly in the hypoxic group, while the Ep in the control group continued to fall to 15 mU/mL on day 21, the last day of pregnancy. Before day 17 of gestation the rat fetus appears to have hypoxia-independent, extrahepatic Ep available which is followed by hepatic and renal Ep production, both of which become sensitive to maternal hypoxia during the last days of pregnancy. In the neonatal rat plasma and tissue, Ep levels varied greatly during the first three weeks of life regardless of whether the animals were hypoxic or not. With the exception of the first and ninth days of life, circulating Ep levels were higher than adult levels in normal newborn rats. Neonatal rats responded to hypoxia with increasing Ep levels, and the response increased with age such that during the third week of life the plasma Ep levels were significantly higher than in adult hypoxic rats. No sex difference in male and female response to hypoxia could be documented until sexual maturity (day 42). In the normoxic neonatal rat more Ep originated from the liver than the kidneys until day 10, while under hypoxic conditions the switch occurred as early as two days after birth.