Creatine and the control of muscle-specific protein synthesis in cardiac and skeletal muscle.

The observation that increased muscular activity leads to muscle hypertrophy is well known, but identification of the biochemical and physiological mechanisms by which this occurs remains an important problem. The hypothesis has been proposed that creatine, an end product of contraction, may be the chemical signal coupling increased muscular activity and increased contractile mass. Two muscle models have been used in experimental tests of this hypothesis: differentiating skeletal muscle cells in culture and the fetal mouse heart in organ culture. Using these culture models, it is possible to alter the intracellular creatine concentration and to measure the effect of increased creatine concentrations on the rates of synthesis and accumulation of both muscle-specific and nonspecific proteins. The results show that muscle-specific protein synthesis in both skeletal and cardiac muscle is selectively stimulated by creatine.