In vitro skeletal muscle protein and RNA incorporation in neuromuscular disease.

Skeletal muscle of Duchenne muscular dystrophy (DMD) patients, DMD carriers and of patients with other neuromuscular diseases was sampled at diagnostic muscle biopsy. The incorporation of isotopic precursors into protein and RNA in a 1-hour in vitro incubation of these samples was then determined. Individual DMD results overlap with these obtained with normal muscle, and an inverse relationship is observed between DMD patient age and incorporation into skeletal muscle protein. The protein and RNA incorporation of DMD carrier skeletal muscle was normal. Limb-girdle dystrophy shows an increase in protein incorporation, while nemaline myopathy, dystrophia myotonica and polymyositis show increases in both protein and RNA incorporation over normal skeletal muscle. The significance of the incorporation observed in the neuromuscular disorders studied in discussed.