Alterations in Hepatic Lipids and Proteins by Chronic Ethanol Intake: A High‐Pressure Fourier Transform Infrared Spectroscopic Study on Alcoholic Liver Disease in the Rat

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Abstract
Using high‐pressure Fourier transform infrared (FT‐IR) spectroscopy, alterations of hepatic lipids and proteins in alcoholic liver disease of the rat were examined. FT‐IR spectra were obtained from the liver tissues of the rats pair‐fed a nutritionally adequate liquid diet and ethanol/dextrose via an implanted intragastric tube for 6 months. The pressure on the liver samples was raised up to 10 kbar, taking FT‐IR spectra at regular increments as the pressure was raised. Total lipids measured by the band derived from the stretching mode of carbonyl groups in lipid (v C=O) were increased 4 times in the liver of ethanol‐fed rats (E) compared with the pair‐fed control rats (C). The frequency of the C=O band of E decreased with increasing pressure, which indicated that hydrogen‐bonding was present on the C–O groups of lipids in E. The intensity of the CH stretching bond of the HC=CH groups was 2.8 times higher in E than that in C, which means that there was an increase in the population of unsaturated double bonds in acyl chains of lipids in E. The conformational structure of the protein molecules was slightly changed in E. The reactivity of carboxylate side groups in proteins observed by reaction with Ba++ ions was higher in E than that in C. These infrared spectroscopic results suggest that chronic ethanol intake induces not only an increase in the amount of total lipid but also changes the composition of lipids and the conformation of protein molecules in the liver of rats.