Studies of Dietary Effects on Free and Membrane-bound Polysomes in Rat Liver

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Abstract
Adult rats of the Sprague-Dawley strain were divided into three groups and fed in the following way: group 1 received ad libitum a complete diet, group 2 received ad libitum a protein-free diet and group 3 was pair-fed with group 2 a complete diet. After 10, 20, or 40 days the animals were killed and free and membrane-bound polysomes prepared and analyzed in sucrose gradients. After 20 days of protein starvation the following modifications appear: 1) preferential breakdown of membrane-bound polysomes with increase of light aggregates; 2) shift of free polysomes toward classes heavier than pentamers; 3) increase of monosomes and disomes in both free and membrane-bound polysomes; 4) imbalance between RNase and RNase inhibitor determined by a decrease of RNase inhibitor; 5) increase of the 45S subribosomal particle. These modifications seem to be an adaptation mechanism for survival in adverse conditions like long-term protein deficiency.