FT-IR spectroscopic investigation of ionizing radiation-induced damage in the small intestine of whole-body irradiated rats

Radiation-induced reactive oxygen species (ROS) initiate a myriad of oxidation reactions in the macromolecules of the biological tissues. ROS are of the primary factors responsible for induction of radiation damage in biomolecules. Polyunsaturated fatty acids (PUFAs) conforming the phospholipid membrane bilayer are highly vulnerable for the ROS attacks due to presence multiple double bonds in the PUFAs structure. The ROS-mediated oxidative degeneration of lipids is called lipid peroxidation. Freeze-dried sections from the small intestines of rats either sham, 10 cGy, 2 Gy-irradiated or rats received 10 cGy 24 h prior to a subsequent dose of 2 Gy, were examined for lipid peroxidation and protein damage using Fourier transform infrared (FT-IR) spectroscopy in spectral range 400-4000 cm(-1). Our FT-IR data prove the induction of lipid peroxidation and disorder in the unsaturated lipids in the samples of all of the irradiated groups as compared with the sham-irradiated group. Lipid peroxidation was evident by the decrease in total lipid content, decrease of un-saturation level of lipids marked by the increase in the ratio saturated/unsaturated acyl chains and decrease of the integrated area under the olefinic=CH absorption band. This effect was associated with significant decreases in the length of phospholipid hydrocarbon chains in all of the irradiated groups. The results also suggest a decrease in the fluidity of the cells membrane as well as possible alterations in the secondary structure of proteins. No adaptive response was seen when the 10 cGy dose preceded the 2 Gy dose. However, 10 cGy induced effects comparable to and in some cases higher than the 2 Gy dose. FT-IR spectroscopy was a powerful sensitive tool to investigate the molecular structure of lipids and proteins following x-irradiation and revealed an increase in lipid peroxidation in all irradiated groups associated with increase in the rigidity of the cell membrane and alterations in the protein secondary structure.