鼠离体灌流心脏模型125I-BMIPP与125I-IPPA代谢的对比研究

目的 比较侧链脂肪酸β-甲基碘苯脂十五烷酸(BMIPP)和直链脂肪酸碘苯脂十五烷酸(IPPA)在心肌代谢上的异同和特点.方法 制备大鼠离体灌流心脏模型10只,分为2组,每组5只.基础灌流30 min后,分别于灌流液中加入125I-BMIPP和125I-IPPA,持续灌流3 h后取样灌流液,提取脂溶相处理后行薄层色谱法(TLC)和高压液相色谱法(HPLC)分析,并与加入被测物品初期(5 min)的结果相比较.结果 125I-BMIPP灌流5 min和3 h后脂溶相提取放射性活度分别为注入剂量的99%和92%,而125I-IPPA分别为95%和38%.125I-BMIPP灌流5 min,HPLC分析放射性全部集中于保留时间37 min段.3 h后该处仍呈主峰,其前出现数个小峰,峰值分别对应于代谢产物甲基碘苯脂十四烷酸、对碘苯十二酸、对碘苯十酸、对碘苯八酸、对碘苯六酸、对碘苯四酸和对碘苯乙酸.125I-IPPA灌流初期于HPLC保留时间33 min段显示明显高峰,继续灌流3 h后,该峰值消失.TLC测定125I-BMIPP Rf值为0.52,125I-IPPA为0.45.3 h后,85%的125I-BMIPP仍集中于Rf值0.52处,在Rf值0.31前后有数个小峰.而125I-IPPA持续灌流3 h后Rf值0.45处的峰消失,仅在原点发现放射性.结论 125I-BMIPP不被β氧化,能在心肌细胞内长时间滞留,便于观察脂肪酸在心脏内的分布状况.而125I-IPPA代谢快速,可显示心肌中长链脂肪酸代谢氧化过程.     

离体心脏灌注模型的制备

目的 通过制备大鼠离体心脏灌注模型,探讨模型制备的方法及注意事项.方法 健康成年大鼠20只,雌雄不限,取离体心脏,制备Langendorff模型及离体工作心脏灌注模型.结果 实验中成功18例(成功率90%).心脏均能持续稳定搏动,心脏收缩有力,左室内压为7.1～10.5 kPa,处于生理范围(6.3～10.3 kPa),心率250～300 /min,心律齐,心脏可平稳跳动6 h以上.结论 Langendorff模型及离体工作心脏灌注模型操作方便、稳定,是比较符合生理特性的离体心脏灌注模型.     

呋喃苯胺酸抗离体鼠心再灌注损伤作用的研究

在Langendorff主动脉逆灌装置上初步发现,呋喃苯胺酸(FRM)对心肌缺血后再灌注损伤具有保护作用。FRM保护组(10um/L)冠脉流量及心肌收缩力的恢复程度优于对照组,再灌注心律失常发生率明显低于对照组。但FRM保护作用的剂量依赖性及其潜在的负性肌力作用等问题尚有待进一步研究。     

离体和在体心肌灌注显像的实验研究

为探讨正常心肌的图像特点及胸壁、膈肌对心肌图像的影响,本研究对5只猪进行在体和离体99Ｔｃｍ甲氧基异丁基异腈(ＭＩＢＩ)心肌灌注显像,定量分析和比较左室各部位心肌在2种状态下的放射性及衰减程度,现报告如下。一、材料和方法1在体心肌灌注显像。哈白家猪5只,平均40(3～6)月龄,体重48～55ｋｇ,平均52ｋｇ。静息状态下耳缘静脉注射99ＴｃｍＭＩＢＩ1110ＭＢｑ只,2ｈ后在戊巴比妥钠麻醉状态下仰卧于断层床,前肢充分伸展以保证探头平面贴近胸壁。采用ＴｏｓｈｉｂａＧＣＡ901ＡＳＰＥＣＴ仪,配低能高分辨准直器,旋转半径20ｃｍ,矩阵64×64,…     

正常大鼠离体工作心脏收缩和泵血功能指标的测定分析

报道了82例正常大鼠离体工作心脏收缩和泵血功能指标的测定结果。Vpm为1.85±0.65ml/s,dP/dt_(max)为279±39kPa/s,泵功能指标CO、CF和AF分别为43.2±7.6、8.5±1.2和35.2±4.5ml/min,雌雄间各指标无差异性。Vpm与dP/dt_(max)、LVSP、CO、CF和AF高度相关。对14只大鼠离体工作心脏进行了动态观测,90min内各指标稳定。     

异丙酚对大鼠离体心脏缺血/再灌注损伤时心肌c-fos基因表达的影响

目的观察异丙酚对离体大鼠全心缺血再灌注损伤心肌c-fos基因表达的影响,探讨其对缺血再灌注损伤心肌保护作用机制。方法Wistar大鼠36只,随机分为对照组和异丙酚组,每组又分为缺血前、缺血30min和复灌30min3个亚组。通过离体心肌灌注模型,采用免疫组化及RT-PCR观察心肌c-fos蛋白及c-fo smRNA表达水平的变化。结果与缺血前相比,缺血30min及再灌注30min亚组的c-fos蛋白的光密度值及c-fos mRNA表达水平均增加（P〈0．01）;与对照组相比,异丙酚各亚组的c-fos蛋白光密度值及c-fos mRNA表达水平均降低（P〈0．01）。结论c-fos基因参与了心肌缺血再灌注损伤的基因调节。异丙酚可减轻心肌c-fos基因的表达,并可避免或减轻心肌缺血再灌注损伤。     

影响显像剂在缺血-再灌注心肌中分布的代谢因素

对于心肌显像 ,诸多代谢因素对诊断和研究缺血性心脏病至关重要。笔者在综述缺血 再灌注心肌 (ＩＲＭ)各种代谢异常的基础上 ,对涉及影响99Ｔｃｍ 甲氧基异丁基异腈 (ＭＩＢＩ)、99Ｔｃｍ ｔｅｔｒｏｆｏｓｍｉｎ、2 0 1Ｔｌ、18Ｆ 脱氧葡萄糖 (ＦＤＧ)、12 3 Ｉ 间碘苄胍 (ＭＩＢＧ)和12 3 Ｉ 脂肪酸类似物等常用心肌显像剂分布的代谢因素作一剖析。ＩＲＭ定义为①缺血 :因冠状动脉 (简称冠脉 )血流不足、氧剥夺引起的不能维持稳定代谢状态的一种表现 ;②再灌注损伤 :缺血后冠脉血流恢复引起的以氧自由基产生和离子转运异常为特征的功能损…     

缺血及再灌注大鼠心肌细胞内pH的^31P—核磁共振测定

建立了用＾３１Ｐ－核磁共振（＾３１Ｐ－ＮＭＰ）非损伤性测定大鼠心肌细胞内ｐＨ（ｐＨｉ）的方法，并用该方法研究了Ｌａｎｇｅｎｄｏｒｆｆ灌流大鼠心脏在常温及低温缺血以及再灌注过程中ｐＨｉ的动态变化过程。     

急性心肌梗死再灌注治疗前后心肌血流和代谢的变化及临床意义

目的　探讨急性心肌梗死患者行经皮冠状动脉腔内成形术 (PTCA)和支架术后心肌血流、脂肪酸代谢及糖代谢的变化及其临床意义。方法　 2 2例急性心肌梗死患者 ,于发病后 4周行延迟PTCA ,术前 (急性期 )及术后 (慢性期 )分别行2 0 1 Tl、1 2 3I β 甲基碘苯脂十五烷酸 (BMIPP)SPECT显像及1 8F 脱氧葡萄糖 (FDG)PET心肌显像。将左心室分成 13个节段 ,采用 4级评分法对2 0 1 Tl、1 2 3I BMIPP显像放射性分布进行视觉评价 ,两者得分差为2 0 1 Tl BMIPP不匹配。在血流减低部位 ,定量测定1 8F FDG摄取。慢性期复查冠状动脉造影。结果　急性期心肌血流 脂肪酸代谢不匹配的节段 ,1 8F FDG摄取率明显高于匹配节段 [(76 .5± 10 .6 ) %和 (4 5 .8± 8.6 ) % ,P <0 .0 1],慢性期两者无明显差异。冠状动脉非再狭窄患者其慢性期2 0 1 Tl BMIPP不匹配 (0 .2 5± 0 .4 2 )及1 8F FDG摄取率 [(5 2 .1± 8.1) % ]较急性期 [0 .36± 0 .5 1和 (72 .8± 9.8) % ]明显降低 (P均 <0 .0 1) ;冠状动脉再狭窄患者其慢性期与急性期比较 ,2 0 1 Tl BMIPP不匹配及1 8F FDG摄取率无明显变化。结论　观察急性心肌梗死PTCA前后心肌血流 脂肪酸代谢及糖代谢的变化 ,可间接预测PTCA后再狭窄。     

Accelerated BMIPP uptake immediately after reperfused ischemia in the isolated rat heart model

Objective  

¹²³I-beta-methyl iodophenyl pentadecanoic acid (BMIPP) can visualize myocardial fatty acid metabolism and has extensive potential for diagnosing cardiac diseases such as acute coronary syndrome in the clinical setting. Increased BMIPP uptake with decreased perfusion occasionally occurs under acute reperfusion ischemia and the kinetics of BMIPP remain unclear. The present study uses the isolated rat heart model to measure kinetic changes in BMIPP under acute reperfusion ischemia.     

Extraction of long-chain fatty acids in isolated rat heart during acute low-flow ischemia.

Although beta-oxidation of fatty acids is suppressed rapidly during ischemia, the behavior of fatty acid extraction at different flow rates is incompletely understood. This study assessed the relationship between flow and extraction of (123)I-iodophenylpentadecanoic acid (IPPA) in the isolated heart model, especially at low flow. METHODS: Isolated hearts from male Wistar rats (n = 15) were subjected to retrograde perfusion with constant flow (Krebs Henseleit solution containing 10 mmol/L glucose). A latex balloon in the left ventricle allowed isovolumetric contractions and ventricular pressure measurements. The extraction of (123)I-IPPA was assessed with the indicator dilution technique and (99m)Tc-albumin as the intravascular reference. The flow was either increased from the control flow (8 mL/min) until 300% or reduced until 10%. (123)I-IPPA extraction was measured three times before and 10 min after flow alteration. The tracer uptake was estimated from the product of net extraction and flow. RESULTS: The mean (123)I-IPPA extraction at the control flow (third measurement) was 51.6% +/- 2.8%. Between flow rates of approximately 25% and 300%, (123)I-IPPA extraction increased exponentially at decreasing flow rates. At flow rates < or =25% of the control flow, (123)I-IPPA extraction was exponentially higher than predicted. (123)I-IPPA uptake and flow changed largely in parallel. During low flow, the rate-pressure product showed the expected decline (perfusion-contraction matching). CONCLUSION: The extraction of (123)I-IPPA is preserved and slightly increased (relative to flow) during acute low-flow ischemia.     

Gadolinium-DTPA-enhanced magnetic resonance imaging of the isolated rat heart after ischemia and reperfusion.

The objective of this study was to assess the potential of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) to identify myocardial ischemia and reperfusion in the isolated rat heart model. Ischemia was induced by reducing the perfusion pressure from 80 to 30 mm Hg for 2 hours. Hearts were not reperfused, or were reperfused for 20 minutes or for 2 hours. Perfusion was performed with Evans blue dye and/or Gd-DTPA for 3 minutes. Twenty isolated rat hearts were perfused according to the Langendorff method, and divided into five groups according to the perfusion status and the use of Gd-DTPA and/or Evans blue as perfusion markers. The Evans blue distribution in the hearts was assessed by point-counting volumetry. The Gd-DTPA distribution was assessed by magnetic resonance microimaging at 6.3 T field strength. Evans blue staining clearly identified areas with "no flow" or "no reflow." Perfusion with Gd-DTPA enhanced signal intensity significantly, both in ischemic and reperfused myocardium. Signal intensity in hearts reperfused for 2 hours was increased significantly compared to nonreperfused ischemic hearts, but not to ischemic hearts reperfused for 20 minutes. Magnetic resonance imaging with the aid of Gd-DTPA can identify ischemia and reperfusion in the isolated rat heart, dependent on residual perfusion.     

Metabolic adaptation to myocardial ischemia: The role of fatty acid imaging

Conclusion  Metabolic adaptation may represent one of the earliest responses to myocardial ischemia, left ventricular remodeling, diabetes, and uremic heart disease. Thus targeting alterations in myocellular metabolism may foster novel and effective therapeutic interventions. In the future, recognizing key intracellular signals that link energy substrate metabolism with gene expression will allow the discovery of more specific molecular targets for the diagnosis and treatment of cardiovascular disease.     

Proton T2 relaxation of cerebral metabolites during transient global ischemia in rat brain

Putative changes of metabolite T₂ relaxation times were investigated before and after a 20-min period of global ischemia in rat brain in vivo (n= 10) using localized proton MRS at different echo times (2.35 T). Neither absolute T₂ relaxation times (TE = 20-270 ms) nor time courses of T₂-weighted metabolite signals (TE = 135 ms) revealed statistically significant changes during the occlusion or early reperfusion relative to pre-ischemic baseline. These findings are in line with reports of relaxation changes at much later stages and further demonstrate that altered T₂ relaxation is not a confounding factor in diffusion-weighted long-TE proton MRS during early ischemic events.     

Influence of global ischemia on intracellular sodium in the perfused rat heart

Intracellular [Na+], [H+], and [ATP] and mechanical performance were measured in the isovolumic perfused rat heart during ischemia. The concentration of intracellular sodium, [Na+]i, was determined by atomic absorption spectroscopy under control conditions, and [Na+]i was monitored by 23Na NMR spectroscopy at 1-min intervals under control conditions and during global ischemia. [ATP], [H+], and [Pi] were measured by 31P NMR in a separate group under identical conditions. The control [Na+]i measured by atomic absorption was 30.7 +/- 3.3 mM (mean +/- SD, n = 6), and [Na+]i measured by NMR was 6.2 +/- 0.5 mM (n = 3). Brief ischemia (10 min) was associated with a 54% increase in [Na+]i which reversed completely with reperfusion. Developed pressure also returned to control values upon reperfusion. Prolonged ischemia (30 min) produced continuous further accumulation of sodium (0.53 mM/min, r2 = 0.99). [H+] also increased approximately linearly early in ischemia (0.084 microM/min, r2 = 0.97). The rate of increase in [Na+]i was more than 4000 times greater than the increase in [H+] on a molar basis. Nevertheless, [H+]/[Na+]i increased early in ischemia because the proportional change in [H+] was greater than that in [Na+]i. These results indicate that (1) intracellular sodium measured by NMR in the functioning heart is about 20% of total intracellular sodium; (2) intracellular acidosis and accumulation of sodium develop simultaneously during global ischemia; (3) increased intracellular sodium content is not in itself an indicator of irreversible injury; and (4) recovery of mechanical performance is associated with return of [Na+]i (measured by NMR) to baseline after brief ischemia. The mechanism of the increase in sodium content detected by NMR is unknown.     

Changes in perfusion and fatty acid metabolism of rat heart with autoimmune myocarditis

To elucidate the change in perfusion and aerobic metabolism in myocarditis, tissue counting and dual tracer ex vivo autoradiography with Tl-201 and a free fatty acid analog, I-123- or I-125-labeled (p-iodophenyl)-methyl-pentadecanoic acid (BMIPP), were performed in rats with myocarditis induced by immunization with cardiac myosin. Inflammatory damage was classified histologically. At the acute stage (2-4 weeks after the antigen-injection), total heart uptakes of Tl and BMIPP and the ratio (BMIPP/Tl) were significantly reduced in myocarditis rats (N = 15) compared with the controls (N = 12). Myocardial distribution of Tl and BMIPP was not homogeneous. Relative uptake of Tl and BMIPP (N = 9, 128 regions) was gradually decreased with the extent of inflammation, and the regional BMIPP/Tl was smaller than the control. At the subacute stage (7 weeks after the antigen-injection), total Tl uptake in myocarditis rats (N = 5) recovered to the control level (N = 4), but that of BMIPP was still significantly lower than the control. BMIPP/Tl was still significantly lower in myocarditis. Myocardial distribution of Tl and BMIPP recovered to be more homogeneous. Relative uptake of Tl and BMIPP (N = 6, 78 regions) still gradually but significantly decreased with the extent of inflammation. Regional BMIPP/Tl was still depressed in myocarditis. These results indicate that myocardial perfusion and aerobic metabolism were discrepant and heterogeneously suppressed with severe inflammation during the acute stages, but the difference decreases with time. Examination with Tl-201 and BMIPP may provide information about the severity of myocarditis.     

beta-Methyl-15-p-iodophenylpentadecanoic acid metabolism and kinetics in the isolated rat heart

The use of 15-p-iodophenyl-beta-methyl-pentadecanoic acid (beta Me-IPPA) as an indicator of long chain fatty acid (LCFA) utilization in nuclear medicine studies was evaluated in the isolated, perfused, working rat heart. Time courses of radioactivity (residue curves) were obtained following bolus injections of both beta Me-IPPA and its straight chain counterpart 15-p-iodophenyl-pentadecanoic acid (IPPA). IPPA kinetics clearly indicated flow independent impairment of fatty acid oxidation caused by the carnitine palmitoyltransferase I inhibitor 2[5(4-chlorophenyl)pentyl]oxirane-2-carboxylate (POCA). In contrast, beta Me-IPPA kinetics were insensitive to changes in fatty acid oxidation rate and net utilization of long chain fatty acid. Analysis of radiolabeled species in coronary effluent and heart homogenates showed the methylated fatty acid to be readily incorporated into complex lipids but a poor substrate for oxidation. POCA did not significantly alter metabolism of the tracer, suggesting that the tracer is poorly metabolized beyond beta Me-IPPA-CoA in the oxidative pathway.     

Gamma-irradiated ceruloplasmin affords antifibrillatory protection against ischemia/reperfusion damage in the isolated rat heart

PURPOSE: Ceruloplasmin (CP), an important serum antioxidant, was previously found to reduce the incidence of ventricular fibrillation (VF) induced by ischemia and reperfusion in isolated rat hearts. The present study investigated whether CP sterilized by gamma-irradiation maintains its antiarrhythmic capacity and in vitro antioxidant properties. MATERIALS AND METHODS: Isolated rat hearts submitted to regional ischemia (15 min), were reperfused (10 min) with native CP or with CP irradiated at various doses (1-3 kGy) in the absence or presence of tyrosine (Tyr). RESULTS: All untreated hearts showed VF at reperfusion, which were all irreversible ventricular fibrillation (IVF). No IVF were found in hearts treated with native CP or gamma-irradiated CP. Cardioprotection afforded by irradiated CP (with or without Tyr) was slightly higher than that obtained with native CP. No VF at all (100% prevention) was found in hearts treated with CP irradiated alone or in the presence of tyrosine at 3 kGy. Tyrosine and irradiated tyrosine had no cardiotoxic or protective effects on reperfusion-induced arrhythmias. The Oxygen Radical Absorbing Capacity (ORAC), measured in vitro with beta-phycoerythrin (beta-PE) fluorescent indicator, was slightly higher for gamma-irradiated CP in the presence of Tyr. CONCLUSIONS: Ceruloplasmin sterilized by gamma-irradiation maintains antioxidant and antiarrhythmic effects in the post-ischemia reperfused isolated rat heart.     

Metabolite and water apparent diffusion coefficients in the isolated rat heart: effects of ischemia.

A decrease in the apparent diffusion coefficient (ADC) of water is important in the detection of acute brain disorders, yet it is unknown whether changes in myocardial ADCs hold similar potential. Consequently, in this study a STEAM pulse sequence was modified in order to measure the ADCs of water and the (1)H-NMR detectable metabolites, taurine (an inert marker) and creatine, during perfusion, ischemia, and reperfusion in the isolated rat heart. At the short diffusion time of 50 ms, myocardial ADCs were (1.06 +/- 0. 07) x 10(-3) mm(2)/s for water, (0.29 +/- 0.01) x 10(-3) mm(2)/s for taurine and (0.26 +/- 0.01) x 10(-3) mm(2)/s for creatine. Heart water and taurine ADCs remained constant during ischemia, yet the total creatine ADC increased by 35% owing to the hydrolysis of PCr to creatine. The average cardiomyocyte diameter, calculated from taurine ADC values measured at diffusion times between 50 ms and 1510 ms, was 40 microm in the perfused heart and 27 microm by the end of ischemia. It is concluded that the taurine ADC measured at short diffusion times does not reveal ischemic injury in the heart, but at long diffusion times may be used to calculate changes in myocyte diameter. Magn Reson Med 44:208-214, 2000.