Creatine: a possible stimulus skeletal cardiac muscle hypertrophy.

These experiments test whether creatine, a product of muscular contraction, stimulates myofibrillar protein synthesis. It was found that skeletal muscle cells formed both in vitro and in vivo and cardiac muscle cells formed in vivo synthesize myofibrillar proteins faster when supplied creatine in vitro. The rates of synthesis and/or accumulation of three myofibrillar proteins-myosin heavy chain actin, and creatine kinase-were stimulated by creatine. In contrast, the rates of synthesis of total protein and of deoxyribonucleic acid (DNA) and the activities of several nonmyofibrillar enzymes were not altered by creatine. These include lactic dehydrogenase, cathepsin D, acid phosphatase, and beta-acetylglucosaminidase. It is concluded that creatine selectively stimulated the rate of synthesis of contractile proteins in skeletal and cardiac muscle in vitro and may play a role in muscle hypertrophy.