Falkensammer Juergen, Stojakovic Tatjana, Huber Kurt, Hammerer-Lercher Angelika, Gruber Ingrid, Scharnagl Hubert, Fraedrich Gustav, Santner Wolfram, Schocke Michael, Greiner Andreas
Division of Vascular Surgery, Medical University Innsbruck, Innsbruck, and 3rd Medical Department, Cardiology and Emergency Medicine, Wilhelminenhospital Vienna, Austria.
Clin Chem Lab Med. 2007;45(4):535-40. doi: 10.1515/CCLM.2007.087.
Ischemia-modified albumin (IMA) is an emerging marker of ischemia. To investigate the applicability of IMA for the diagnosis of skeletal muscle ischemia, we examined IMA changes as measured by the albumin-cobalt binding test, in a group of healthy volunteers after standardized exercise-induced calf muscle ischemia.
A total of 12 healthy volunteers underwent standardized exercise on a plantar flexion pedal. Ischemic conditions were achieved by inflating a femoral blood pressure cuff at incremental pressures of 0, 60, 90, 120 and 150 mm Hg. Calf muscle ischemia was identified by synchronous 31P magnetic resonance spectroscopy, measuring intracellular concentrations of phosphocreatine (PCr) and inorganic phosphate (Pi). In addition, IMA, serum albumin, lactate, troponin T (TnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) were measured at baseline and at 5, 10, 30, 360 and 720 min after cuff release.
Magnetic resonance spectroscopy showed calf muscle ischemia in all participants upon exercise and cuff inflation. Circulating IMA concentrations increased significantly after cuff release (p=0.03) and returned to baseline within 30 min. While we found a significant negative correlation with albumin, there was no association of IMA levels with lactate or intracellular levels of PCr or Pi in samples obtained at baseline and post-ischemia. TnT and NT-proBNP remained within the normal range throughout the observation period in all participants.
IMA may represent a clinical marker for skeletal muscle ischemia, although its lack of specificity requires careful clinical interpretation of data. The short period of IMA elevation after ischemic exercise requires standardized conditions for use as a diagnostic tool and hints at IMA applicability as a marker of prolonged or chronic ischemia.
缺血修饰白蛋白（IMA）是一种新兴的缺血标志物。为了研究IMA在骨骼肌缺血诊断中的适用性，我们在一组健康志愿者进行标准化运动诱导的小腿肌肉缺血后，通过白蛋白-钴结合试验检测了IMA的变化。
共有12名健康志愿者在足底屈曲踏板上进行标准化运动。通过在0、60、90、120和150 mmHg的递增压力下充气股动脉血压袖带实现缺血状态。通过同步31P磁共振波谱法确定小腿肌肉缺血，测量细胞内磷酸肌酸（PCr）和无机磷酸盐（Pi）的浓度。此外，在基线以及袖带松开后5、10、30、360和720分钟测量IMA、血清白蛋白、乳酸、肌钙蛋白T（TnT）和N末端前B型利钠肽（NT-proBNP）。
磁共振波谱显示所有参与者在运动和袖带充气后出现小腿肌肉缺血。袖带松开后循环IMA浓度显著升高（p = 0.03），并在30分钟内恢复到基线水平。虽然我们发现IMA与白蛋白呈显著负相关，但在基线和缺血后采集的样本中，IMA水平与乳酸或PCr或Pi的细胞内水平无关。在所有参与者的整个观察期内，TnT和NT-proBNP均保持在正常范围内。
IMA可能是骨骼肌缺血的临床标志物，尽管其缺乏特异性需要对数据进行仔细的临床解读。缺血运动后IMA升高的时间较短，需要标准化条件才能用作诊断工具，这提示IMA可作为长期或慢性缺血的标志物。
