We examined in vivo the effect of dietary fats and oils with different peroxidizability on protein carbonyl content, the presumed index of free radical-mediated protein oxidation. For 15.6 months, SHRSP (stroke-prone spontaneously hypertensive strain) rats were fed a diet supplemented with lard, safflower oil, perilla oil or fish oil/soybean oil, the peroxidizability of which increases in this order. The peroxidizability of tissue lipids was positively correlated with the protein carbonyl content in skeletal muscle, but not in the brain, heart or liver. The protein carbonyl content in the lard group was higher in the brain and liver compared to the other dietary groups. These results contradict the concept that long-term feeding of easily autoxidizable fatty acids allows the accumulation of lipid peroxides to accelerate the development of the free radical diseases, and suggest that tissue protein carbonyl content is not a simple reflection of autoxidizability-related lipid peroxidation but is also influenced by other biochemical processes.
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