Spontaneous Raman spectroscopy, which senses changes in cellular contents of reduced cytochrome c, could be a powerful tool for label-free evaluation of ischemic hearts. However, undetermined is whether it is applicable to evaluation of myocardial viability in ischemic hearts. To address this issue, we investigated sequential changes in Raman spectra of the subepicardial myocardium in the Langendorff-perfused rat heart before and during ligation of the left coronary artery and its subsequent release and re-ligation. Under 532-nm wavelength excitation, the Raman peak intensity of reduced cytochrome c at 747 cm⁻¹ increased quickly after the coronary ligation, and reached a quasi-steady state within 30 min. Subsequent reperfusion of the heart after a short-term (30-min) ligation that simulates reversible conditions resulted in quick recovery of the peak intensity to the baseline. Further re-ligation resulted in resurgence of the peak intensity to nearly the identical value to the first ischemia value. In contrast, reperfusion after prolonged (120-min) ligation that assumes irreversible states resulted in incomplete recovery of the peak intensity, and re-ligation resulted in inadequate resurgence. Electron microscopic observations confirmed the spectral findings. Together, the Raman spectroscopic measurement for cytochrome c could be applicable to evaluation of viability of the ischemic myocardium without labeling.

自发拉曼光谱技术可检测还原的细胞色素c的细胞含量变化，可能是无标记评估缺血性心脏的有力工具。但是，尚不确定它是否适用于评估缺血性心脏的心肌生存能力。为了解决这个问题，我们研究了在结扎左冠状动脉之前和期间以及随后释放和重新结扎之前，在Langendorff灌注大鼠心脏中心外膜下心肌的拉曼光谱的顺序变化。在532 nm波长激发下，还原的细胞色素c在747 cm ^-1的拉曼峰强度冠状动脉结扎后迅速增加，并在30分钟内达到准稳态。短期（30分钟）结扎后模拟可逆性状况，随后的心脏再灌注导致峰值强度快速恢复至基线。进一步的重新连接导致峰强度恢复到与第一局部缺血值几乎相同的值。相比之下，长时间（120分钟）结扎（假定为不可逆状态）后的再灌注导致峰强度的恢复不完全，而再结扎导致回潮不足。电子显微镜观察证实了光谱发现。总之，细胞色素c的拉曼光谱测量可用于评估缺血心肌的生存能力，而无需标记。