Biochemical changes in progressive muscular dystrophy. X. Studies on the biosynthesis of protein and RNA in cellular fractions of the skeletal muscle of normal and vitamin E deficient rabbits.

Abstract

Present investigation was undertaken to elucidate the metabolism of protein and nucleic acids in the skeletal muscle of control and vitamin E deficient rabbits. In order to attain this objective, the content and synthesis of protein and RNA were measured in the homogenate and various subcellular fractions of the skeletal muscle of control and vitamin E deficient rabbits. Our results indicate a possibility of reduction in the muscle volume in the dystrophic muscle since the content of DNA and RNA did not change in such muscles. The protein content, however, decreased considerably in the dystrophic muscle.Incorporation studies indicated a considerable increase in the synthesis of protein and RNA. It was also observed that the excretion of radioactivity was much higher in the urine of dystrophic animals. These findings indicate a rapid turnover of protein in the dystrophic muscle.The sucrose density gradient analysis of polysomal material from the dystrophic muscle indicated a lowering in the concentration of heavier polysomes synthesizing myosin and a considerable increase in the region of lighter polysomes synthesizing tropomyosin. From these findings it is speculated that vitamin E may play an important role in the synthesis of specific muscle proteins. Addition of 250 μg of poly-U restored the polysomal content of dystrophic muscle to that of control, leading to the hypothesis that vitamin E deficient rabbit muscle may be lacking in the messenger RNA content.