Preliminary study on fatal hyperthermia in rat liver tissue by Fourier transform infrared microspectroscopy

Despite the progress that has been made during the past several decades in forensic pathology, post-mortem diagnosis of hyperthermia remains difficult. The current study aimed to investigate the spectral changes in rat liver under hyperthermic conditions compared with the control groups of fatal asphyxiation, brainstem injury, and massive haemorrhage, using Fourier transform infrared (FTIR) microspectroscopy. Forty Sprague-Dawley rats were randomly divided into four groups: hyperthermia; asphyxiation; brainstem injury; and massive haemorrhage. The absorbance of ten major absorption bands (1238, 1307, 1396, 1454, 1540, 2850, 2919, 2958, 3070 and 3290cm(-1)) was significant higher in the hyperthermia group compared with the groups of asphyxiation, brainstem injury and massive haemorrhage. The band absorbance ratios of A(2958)/A(2850) and A(1650)/A(1540) were significantly lower, whereas the A(1454)/A(1238), A(1396)/A(1238) and A(1307)/A(1238) ratios were significantly higher in the hyperthermia group compared with the other three causes of death. The frequency of 3290cm(-1) was significantly lower in the hyperthermia group compared with the other three causes of death. Further, using PCA, we demonstrated that infrared spectra extracted from different groups were distinct from each other. These results suggest that FTIR microspectroscopy is a useful technique for discriminating hyperthermia from other causes of death.